| 0/0 |
2026/07/17 00:11 |
flow |
assessment-security |
45m
Results: map[DenialOfService:true Explanation:**Analysis:**
The bug is a `vmalloc` out-of-bounds write in the `vivid` V4L2 test driver
(`drivers/media/test-drivers/vivid/`).
**Root Cause:**
The issue stems from a mismatch between the buffer size calculation and the
image width used during rendering.
1. A user can call `VIDIOC_S_FMT` to set a very small format resolution (e.g.,
16x16). This sets a correspondingly small `bytesperline` (stride) for the image
planes.
2. The user then calls `VIDIOC_S_SELECTION` (with `V4L2_SEL_TGT_CROP` or
`V4L2_SEL_TGT_COMPOSE`) to set a much larger crop/compose rectangle (e.g., 4096
width). The driver updates `dev->fmt_cap_rect` and `dev->compose_cap` to this
larger size but **fails to update `bytesperline`** to accommodate the new width.
3. When `VIDIOC_REQBUFS` is called to allocate buffers, `vid_cap_queue_setup()`
calculates the required buffer size based on the small `bytesperline`. This
results in a small `vmalloc` allocation (e.g., 1 page / 4096 bytes).
4. During streaming, the test pattern generator (`tpg_fill_plane_buffer`)
calculates the number of bytes to write per line (`img_width`) based on the
enlarged `compose.width`.
5. This results in `memcpy()` writing a large amount of data (e.g., 5120 bytes)
into the small allocated buffer (4096 bytes), causing a `vmalloc` out-of-bounds
write.
**Security Impact:**
- **Exploitable & Denial of Service:** The bug allows an attacker to perform an
out-of-bounds write in `vmalloc` memory with a controlled size. This memory
corruption can be leveraged to corrupt adjacent `vmalloc` allocations,
potentially leading to privilege escalation or a kernel panic (Denial of
Service).
- **Unprivileged Access:** The `vivid` driver is a virtual test driver
(`CONFIG_VIDEO_VIVID`). It is not enabled in production kernels, nor is it
auto-loaded by the kernel since it lacks hardware IDs. Furthermore, even if it
were manually loaded, access to `/dev/videoX` nodes is typically restricted to
the `video` group or local logged-in users via ACLs. Therefore, this bug is not
reachable by a typical unprivileged process on a standard production system. Exploitable:true FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 1/1 |
2026/07/17 00:11 |
action |
syz-repro-to-c-repro |
0m
Results:
|
| 2/1 |
2026/07/17 00:11 |
action |
kernel-checkouter |
1m
Results: map[KernelSrc:/app/workdir/cache/src/616ad0bb7fd0e57794f58b6a8b531efba9cc084f]
|
| 3/1 |
2026/07/17 00:12 |
action |
kernel-builder |
16m
Results: map[KernelObj:/app/workdir/cache/build/7e4e2f34249e4ec5e2d57be3eb0d15b08867bc68]
|
| 4/1 |
2026/07/17 00:29 |
action |
codesearch-prepare |
14m
Results: map[Index:codesearch-index]
|
| 5/1 |
2026/07/17 00:43 |
agent |
expert |
13m
Model:
Results: map[DenialOfService:true Exploitable:true FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
Instruction: You are an experienced Linux kernel security engineer. Your task is to analyze given kernel bug report
and determine its security impact based on the following dimensions.
Use the provided tools to examine the source code, check for capability checks (e.g., capable(), ns_capable()),
and understand the nature of the bug. Analyze the given kernel build and configuration.
You can check the kernel config by grepping ".config" file; you can check kernel cmdline by grepping
".config" file for "CONFIG_CMDLINE=". Assume sysctl parameters have default values.
But analyze for the corresponding production build w/o debugging tools enabled (like KASAN, KMSAN, UBSAN).
Try different strategies when analyzing the bug:
- think of ways in which the vulnerable code is unreachable
- or the other way around: try to come up with different ideas of how an unprivileged user can reach the bug
If still unsure err on the side of the bug being non-exploitable/not-accessible.
In the final reply, provide a reasoning for your assessment.
Analysis dimensions:
* Exploitable:
Determine if the bug can result in memory corruption, elevated privileges, or an information leak.
Memory safety issues are almost always exploitable (KASAN or UBSAN reports for use-after-free, out-of-bounds;
refcounting issues, corrupted lists, etc). When kernel is crashing on a completely wild pointer access
(e.g. user-space address, or non-canonical address, but not on NULL or address corresponding to KASAN shadow
for NULL address), including both data accesses and control transfers, that also usually implies possibility
of exploitation. Such reports usually say "unable to handle kernel paging request".
Uses of uninitialized values detected by KMSAN may be exploitable b/c attacker frequently can affect uninit
values with spraying techniques. However, for these exploitability depends on how exactly the uninit value
is used in the code, and what it affects.
Information leaks are exploitable on their own and should be classified as such. A bug that copies kernel
memory contents to userspace (e.g. an out-of-bounds read whose result is returned to the caller, or
uninitialized stack/heap bytes written to a user buffer) is exploitable: it can reveal kernel pointer
values and defeat KASLR, expose sensitive data such as cryptographic keys or other processes' memory, and
serves as a necessary building block in most modern kernel privilege-escalation exploit chains. Do not classify
an information leak as non-exploitable solely because it does not directly cause a memory write or control-flow
hijack; the leak itself is the exploit primitive.
Think of what happens after the bug is triggered. Some bugs cause kernel panic and halt execution,
they are harder to exploit. For example, BUG reports halts the kernel. However, WARNING reports don't halt
execution in production builds. Debug bug detection tools (like KASAN, KMSAN, KCSAN, UBSAN) are also not enabled
in production builds, so attacker can freely exploit these bugs w/o being detected by these tools.
If you see an integer overflow, think how the overflowed value used later (if it's used as allocation size,
or an array index). If you see an out-of-bounds read, think if it's followed by an out-of-bounds write as well.
Some KCSAN data-races may be exploitable by skilled attackers as well. Think what data structures got corrupted
as the result of data races and how. However, note that kernel has lots of "benign" data races that don't lead
to any runtime misbehavior at all.
* Denial Of Service:
Determine if the bug can result in denial-of-service. Most bugs can, since they cause system crash,
hangs, deadlocks, or resource leaks. This is mostly applicable to WARNING bugs that won't cause system crash
in production. For these think what will be consequences of the violation of the kernel assumptions flagged
by the WARNING. In some cases the unexpected condition is also properly handled by the normal control flow
(e.g. with "if (WARN_ON(...))"), these won't cause denial-of-service. If the condition is not handled,
then it may or may not cause denial-of-service.
* Accessible From Unprivileged Processes:
Determine if the bug can be reached from a typical (non-root) user process that does NOT have any special capabilities
(like CAP_SYS_ADMIN, CAP_NET_ADMIN, CAP_NET_RAW, CAP_PERFMON) or access to device nodes restricted to root.
Assume that unprivileged_bpf_disabled=1, that is eBPF loading is not accessible. However, cBPF (classical BPF)
is still accessible to non-root processes.
Assume that user namespaces are not accessible, that is, the process cannot get the mentioned capabilities even
within a new user namespace (checked by ns_capable() function in the kernel sources).
* Accessible From User Namespaces:
Determine if the bug can be reached within a user-namespace where the process has all capabilities
(including CAP_SYS_ADMIN, CAP_NET_ADMIN, CAP_NET_RAW, CAP_PERFMON). Such capabilities are checked with ns_capable()
function in the kernel sources.
* VM Guest Trigger:
Determine if the bug can be triggered from the context of a typical KVM guest (e.g., set up by a QEMU VMM).
Consider accesses to standard Linux host paravirtualized features (virtio-blk, virtio-net, etc.),
and handling of VM exits in the KVM code.
* VM Host Trigger in The Confidential Computing Context:
Determine if the bug can be triggered in a confidential computing guest kernel from the context of a KVM host.
Consider access to standard Linux guest paravirtualized features (virtio-blk, virtio-net, etc.).
* Ethernet Network Trigger:
Determine if the bug can be triggered by processing ingress network Ethernet traffic, either directly (network stack)
or via drivers exposed to network data.
* Other Remote Trigger:
Determine if the bug can be triggered by processing remote traffic other than Ethernet (Wifi, Bluetooth, NFC, etc).
* Peripheral Trigger:
Determine if the bug can be triggered via an untrusted peripheral device that can be physically plugged
into a system, such as a USB device or a niche hardware driver handling external hardware inputs.
This is particularly important for mobile and desktop environments where users can plug in unknown devices.
* Malicious Filesystem Trigger:
Determine if the bug can be triggered by the kernel mounting and parsing a malicious filesystem image.
This is highly critical for Desktop and Mobile environments where external media or downloaded images
might be auto-mounted.
Don't make assumptions about the kernel source code (it may be different from what you assume it is).
Extensively use the provided code access tools (codesearch-*, git-*, grepper, etc)
to examine the actual source code, and confirm any assumptions.
Prefer calling several tools at the same time to save round-trips.
Use set-results tool to provide results of the analysis.
It must be called exactly once before the final reply.
Ignore results of this tool.
Prompt:
The kernel bug report is:
==================================================================
BUG: KASAN: vmalloc-out-of-bounds in tpg_fill_plane_pattern drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2624 [inline]
BUG: KASAN: vmalloc-out-of-bounds in tpg_fill_plane_buffer+0x209a/0x4160 drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2705
Write of size 5120 at addr ffffc90004b01000 by task vivid-000-vid-c/21738
CPU: 0 UID: 0 PID: 21738 Comm: vivid-000-vid-c Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
Call Trace:
<TASK>
__dump_stack lib/dump_stack.c:94 [inline]
dump_stack_lvl+0x100/0x190 lib/dump_stack.c:120
print_address_description mm/kasan/report.c:378 [inline]
print_report+0x13d/0x4b0 mm/kasan/report.c:482
kasan_report+0xdf/0x1c0 mm/kasan/report.c:595
check_region_inline mm/kasan/generic.c:186 [inline]
kasan_check_range+0x10f/0x1e0 mm/kasan/generic.c:200
__asan_memcpy+0x3c/0x60 mm/kasan/shadow.c:106
tpg_fill_plane_pattern drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2624 [inline]
tpg_fill_plane_buffer+0x209a/0x4160 drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2705
vivid_fillbuff+0x963/0x3ff0 drivers/media/test-drivers/vivid/vivid-kthread-cap.c:470
vivid_thread_vid_cap_tick+0x81b/0x1470 drivers/media/test-drivers/vivid/vivid-kthread-cap.c:629
vivid_thread_vid_cap+0x454/0xd70 drivers/media/test-drivers/vivid/vivid-kthread-cap.c:767
kthread+0x370/0x450 kernel/kthread.c:436
ret_from_fork+0x72b/0xd50 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
</TASK>
The buggy address belongs to a
1-page vmalloc region starting at 0xffffc90004b01000 allocated at vb2_vmalloc_alloc+0x135/0x410 drivers/media/common/videobuf2/videobuf2-vmalloc.c:47
The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0xffff88810c0e7000 pfn:0x10c0e7
flags: 0x57ff00000000000(node=1|zone=2|lastcpupid=0x7ff)
raw: 057ff00000000000 0000000000000000 dead000000000122 0000000000000000
raw: ffff88810c0e7000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x102dc2(GFP_HIGHUSER|__GFP_ZERO|__GFP_NOWARN), pid 21737, tgid 21735 (syz.4.4295), ts 400198812927, free_ts 400198788980
set_page_owner include/linux/page_owner.h:32 [inline]
post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1859
prep_new_page mm/page_alloc.c:1867 [inline]
get_page_from_freelist+0xf48/0x3530 mm/page_alloc.c:3946
__alloc_frozen_pages_noprof+0x299/0x2dc0 mm/page_alloc.c:5304
__alloc_pages_noprof mm/page_alloc.c:5338 [inline]
alloc_pages_bulk_noprof+0x5de/0x13c0 mm/page_alloc.c:5230
alloc_pages_bulk_mempolicy_noprof+0x255/0x1270 mm/mempolicy.c:2798
vm_area_alloc_pages mm/vmalloc.c:3714 [inline]
__vmalloc_area_node mm/vmalloc.c:3892 [inline]
__vmalloc_node_range_noprof+0x69d/0x1630 mm/vmalloc.c:4082
vmalloc_user_noprof+0x9e/0xe0 mm/vmalloc.c:4237
vb2_vmalloc_alloc+0x135/0x410 drivers/media/common/videobuf2/videobuf2-vmalloc.c:47
__vb2_buf_mem_alloc drivers/media/common/videobuf2/videobuf2-core.c:242 [inline]
__vb2_queue_alloc+0x8d5/0x1160 drivers/media/common/videobuf2/videobuf2-core.c:523
vb2_core_reqbufs+0x899/0xf30 drivers/media/common/videobuf2/videobuf2-core.c:958
__vb2_init_fileio+0x32d/0x1000 drivers/media/common/videobuf2/videobuf2-core.c:2879
vb2_core_poll+0x611/0x740 drivers/media/common/videobuf2/videobuf2-core.c:2713
vb2_poll+0x4b/0xe0 drivers/media/common/videobuf2/videobuf2-v4l2.c:979
vb2_fop_poll+0x10e/0x350 drivers/media/common/videobuf2/videobuf2-v4l2.c:1245
v4l2_poll+0x15f/0x220 drivers/media/v4l2-core/v4l2-dev.c:350
vfs_poll include/linux/poll.h:82 [inline]
do_pollfd fs/select.c:877 [inline]
do_poll fs/select.c:920 [inline]
do_sys_poll+0x6e5/0xe90 fs/select.c:1015
page last free pid 21737 tgid 21735 stack trace:
reset_page_owner include/linux/page_owner.h:25 [inline]
__free_pages_prepare mm/page_alloc.c:1406 [inline]
__free_frozen_pages+0x79f/0x1090 mm/page_alloc.c:2950
__kasan_populate_vmalloc_do mm/kasan/shadow.c:393 [inline]
__kasan_populate_vmalloc+0x1ea/0x210 mm/kasan/shadow.c:424
kasan_populate_vmalloc include/linux/kasan.h:580 [inline]
alloc_vmap_area+0x95d/0x2bb0 mm/vmalloc.c:2123
__get_vm_area_node+0x1ca/0x330 mm/vmalloc.c:3226
__vmalloc_node_range_noprof+0x228/0x1630 mm/vmalloc.c:4042
vmalloc_user_noprof+0x9e/0xe0 mm/vmalloc.c:4237
vb2_vmalloc_alloc+0x135/0x410 drivers/media/common/videobuf2/videobuf2-vmalloc.c:47
__vb2_buf_mem_alloc drivers/media/common/videobuf2/videobuf2-core.c:242 [inline]
__vb2_queue_alloc+0x8d5/0x1160 drivers/media/common/videobuf2/videobuf2-core.c:523
vb2_core_reqbufs+0x899/0xf30 drivers/media/common/videobuf2/videobuf2-core.c:958
__vb2_init_fileio+0x32d/0x1000 drivers/media/common/videobuf2/videobuf2-core.c:2879
vb2_core_poll+0x611/0x740 drivers/media/common/videobuf2/videobuf2-core.c:2713
vb2_poll+0x4b/0xe0 drivers/media/common/videobuf2/videobuf2-v4l2.c:979
vb2_fop_poll+0x10e/0x350 drivers/media/common/videobuf2/videobuf2-v4l2.c:1245
v4l2_poll+0x15f/0x220 drivers/media/v4l2-core/v4l2-dev.c:350
vfs_poll include/linux/poll.h:82 [inline]
do_pollfd fs/select.c:877 [inline]
do_poll fs/select.c:920 [inline]
do_sys_poll+0x6e5/0xe90 fs/select.c:1015
__do_sys_ppoll fs/select.c:1112 [inline]
__se_sys_ppoll fs/select.c:1092 [inline]
__x64_sys_ppoll+0x2b5/0x350 fs/select.c:1092
Memory state around the buggy address:
ffffc90004b01f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
ffffc90004b01f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffc90004b02000: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
^
ffffc90004b02080: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
ffffc90004b02100: f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8 f8
==================================================================
Reply: **Analysis:**
The bug is a `vmalloc` out-of-bounds write in the `vivid` V4L2 test driver (`drivers/media/test-drivers/vivid/`).
**Root Cause:**
The issue stems from a mismatch between the buffer size calculation and the image width used during rendering.
1. A user can call `VIDIOC_S_FMT` to set a very small format resolution (e.g., 16x16). This sets a correspondingly small `bytesperline` (stride) for the image planes.
2. The user then calls `VIDIOC_S_SELECTION` (with `V4L2_SEL_TGT_CROP` or `V4L2_SEL_TGT_COMPOSE`) to set a much larger crop/compose rectangle (e.g., 4096 width). The driver updates `dev->fmt_cap_rect` and `dev->compose_cap` to this larger size but **fails to update `bytesperline`** to accommodate the new width.
3. When `VIDIOC_REQBUFS` is called to allocate buffers, `vid_cap_queue_setup()` calculates the required buffer size based on the small `bytesperline`. This results in a small `vmalloc` allocation (e.g., 1 page / 4096 bytes).
4. During streaming, the test pattern generator (`tpg_fill_plane_buffer`) calculates the number of bytes to write per line (`img_width`) based on the enlarged `compose.width`.
5. This results in `memcpy()` writing a large amount of data (e.g., 5120 bytes) into the small allocated buffer (4096 bytes), causing a `vmalloc` out-of-bounds write.
**Security Impact:**
- **Exploitable & Denial of Service:** The bug allows an attacker to perform an out-of-bounds write in `vmalloc` memory with a controlled size. This memory corruption can be leveraged to corrupt adjacent `vmalloc` allocations, potentially leading to privilege escalation or a kernel panic (Denial of Service).
- **Unprivileged Access:** The `vivid` driver is a virtual test driver (`CONFIG_VIDEO_VIVID`). It is not enabled in production kernels, nor is it auto-loaded by the kernel since it lacks hardware IDs. Furthermore, even if it were manually loaded, access to `/dev/videoX` nodes is typically restricted to the `video` group or local logged-in users via ACLs. Therefore, this bug is not reachable by a typical unprivileged process on a standard production system.
|
| 6/2 |
2026/07/17 00:43 |
llm |
expert |
0m
Model:
Tokens:
input: 8875
output: 54
thoughts: 188
Thoughts: **KASAN vmalloc-out-of-Bounds Write Investigation**
Okay, I've got a KASAN report pointing to a vmalloc-out-of-bounds write within the `tpg_fill_plane_pattern` function. The culprit is at `drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2624`, and the write size is a rather large 5120 bytes. The offending task is identified as `vivid-000-vid-c`. That's a Video4Linux test pattern generator, which is not surprising. The call trace shows a clear path: it's `tpg_fill_plane_pattern` that's the immediate problem, but it's called from `tpg_fill_plane_buffer`, which is then called by `vivid_fillbuff`. That function is then used within the vivid capture thread.
My next step is to head straight to `drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2624` and the surrounding code. I need to understand what's happening at that line. I'll need to scrutinize the `tpg_fill_plane_pattern` function to see what memory region is being written to, what the source of the write data is, and what the buffer's bounds are. The fact that it's a vmalloc region is useful, but also points toward potential issues with either allocation size or indexing into the allocated region. This requires a close look at the data being used in this area, including the dimensions of the plane. The `vivid_fillbuff` function is also important to understand where the plane data is getting its size and allocation info.
|
| 7/2 |
2026/07/17 00:43 |
tool |
read-file |
0m
Args: map[File:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c FirstLine:2600 LineCount:50]
Results: map[Contents:2600: switch (tpg->field) {
2601: case V4L2_FIELD_INTERLACED:
2602: case V4L2_FIELD_INTERLACED_TB:
2603: case V4L2_FIELD_SEQ_TB:
2604: case V4L2_FIELD_SEQ_BT:
2605: if (even)
2606: memcpy(vbuf, linestart_top, img_width);
2607: else
2608: memcpy(vbuf, linestart_bottom, img_width);
2609: break;
2610: case V4L2_FIELD_INTERLACED_BT:
2611: if (even)
2612: memcpy(vbuf, linestart_bottom, img_width);
2613: else
2614: memcpy(vbuf, linestart_top, img_width);
2615: break;
2616: case V4L2_FIELD_TOP:
2617: memcpy(vbuf, linestart_top, img_width);
2618: break;
2619: case V4L2_FIELD_BOTTOM:
2620: memcpy(vbuf, linestart_bottom, img_width);
2621: break;
2622: case V4L2_FIELD_NONE:
2623: default:
2624: memcpy(vbuf, linestart_older, img_width);
2625: break;
2626: }
2627: }
2628:
2629: void tpg_fill_plane_buffer(struct tpg_data *tpg, v4l2_std_id std,
2630: unsigned p, u8 *vbuf)
2631: {
2632: struct tpg_draw_params params;
2633: unsigned factor = V4L2_FIELD_HAS_T_OR_B(tpg->field) ? 2 : 1;
2634:
2635: /* Coarse scaling with Bresenham */
2636: unsigned int_part = (tpg->crop.height / factor) / tpg->compose.height;
2637: unsigned fract_part = (tpg->crop.height / factor) % tpg->compose.height;
2638: unsigned src_y = 0;
2639: unsigned error = 0;
2640: unsigned h;
2641:
2642: tpg_recalc(tpg);
2643:
2644: params.is_tv = std;
2645: params.is_60hz = std & V4L2_STD_525_60;
2646: params.twopixsize = tpg->twopixelsize[p];
2647: params.img_width = tpg_hdiv(tpg, p, tpg->compose.width);
2648: params.stride = tpg->bytesperline[p];
2649: params.hmax = (tpg->compose.height * tpg->perc_fill) / 100;
]
|
| 8/2 |
2026/07/17 00:43 |
llm |
expert |
0m
Model:
Tokens:
input: 10371
output: 48
thoughts: 117
Thoughts: **Debugging a Memory Copy Issue**
Okay, so I've got a crash, and it's pinpointed right here in `memcpy`. The debugger says it's at line 2624, specifically within `memcpy(vbuf, linestart_older, img_width);`. The size being copied is `img_width`, which I see is 5120. Hmm, the destination, `vbuf`, is apparently out of bounds. That's not good. A quick calculation tells me the allocation for `vbuf` is just a single page, 4096 bytes, but we're attempting to write 5120 bytes. That explains the overrun! Now, I need to trace back where `vbuf` is coming from. Let's see... it looks like `tpg_fill_plane_buffer` is the function that's ultimately responsible, and it's called from `vivid_fillbuff`. That's where I need to start digging to understand how this buffer is being set up and why the size is wrong.
|
| 9/2 |
2026/07/17 00:44 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-kthread-cap.c FirstLine:450 LineCount:50]
Results: map[Contents: 450:
451: if (out_dev)
452: vivid_precalc_copy_rects(dev, out_dev);
453:
454: for (p = 0; p < tpg_g_planes(tpg); p++) {
455: void *vbuf = plane_vaddr(tpg, buf, p,
456: tpg->bytesperline, tpg->buf_height);
457:
458: /*
459: * The first plane of a multiplanar format has a non-zero
460: * data_offset. This helps testing whether the application
461: * correctly supports non-zero data offsets.
462: */
463: if (p < tpg_g_buffers(tpg) && dev->fmt_cap->data_offset[p]) {
464: memset(vbuf, dev->fmt_cap->data_offset[p] & 0xff,
465: dev->fmt_cap->data_offset[p]);
466: vbuf += dev->fmt_cap->data_offset[p];
467: }
468: tpg_calc_text_basep(tpg, basep, p, vbuf);
469: if (!out_dev || vivid_copy_buffer(dev, out_dev, p, vbuf, buf))
470: tpg_fill_plane_buffer(tpg, vivid_get_std_cap(dev),
471: p, vbuf);
472: }
473: if (out_dev && dev != out_dev)
474: mutex_unlock(&out_dev->mutex);
475:
476: dev->must_blank[buf->vb.vb2_buf.index] = false;
477:
478: /* Updates stream time, only update at the start of a new frame. */
479: if (dev->field_cap != V4L2_FIELD_ALTERNATE ||
480: (dev->vid_cap_seq_count & 1) == 0)
481: dev->ms_vid_cap =
482: jiffies_to_msecs(jiffies - dev->jiffies_vid_cap);
483:
484: ms = dev->ms_vid_cap;
485: if (dev->osd_mode <= 1) {
486: snprintf(str, sizeof(str), " %02d:%02d:%02d:%03d %u%s",
487: (ms / (60 * 60 * 1000)) % 24,
488: (ms / (60 * 1000)) % 60,
489: (ms / 1000) % 60,
490: ms % 1000,
491: buf->vb.sequence,
492: (dev->field_cap == V4L2_FIELD_ALTERNATE) ?
493: (buf->vb.field == V4L2_FIELD_TOP ?
494: " top" : " bottom") : "");
495: tpg_gen_text(tpg, basep, line++ * line_height, 16, str);
496: }
497: if (dev->osd_mode == 0) {
498: snprintf(str, sizeof(str), " %dx%d, input %d ",
499: dev->src_rect.width, dev->src_rect.height, dev->input);
]
|
| 10/2 |
2026/07/17 00:44 |
llm |
expert |
0m
Model:
Tokens:
input: 11763
output: 35
thoughts: 48
Thoughts: Okay, here's my interpretation of those thoughts, tailored for an expert audience:
**Analyzing Video Buffer Allocation in the V4L2 Framework**
Alright, let's break this down. My initial thought is to confirm how the buffer is actually allocated. I see it's using `vb2_vmalloc_alloc`. That immediately tells me we're dealing with virtual memory and a likely `vmalloc` based allocation within the kernel. Good, that's the standard approach for this.
Next, I need to understand how the *size* of this buffer is determined. My instinct is that this is influenced by the request parameters. I see that the function `vb2_core_reqbufs` comes into play here. It seems that this function is how the requested buffer parameters determine the sizing.
Now, my focus shifts to the video driver in question, `vivid`. I need to figure out how `vivid` specifically configures its buffer sizes within that `reqbufs` process. Is it using fixed sizes, or is it dynamically calculating them based on the stream's resolution, pixel format, and any other relevant configurations? Understanding the interplay between `vivid`'s configuration and `vb2_core_reqbufs` will be critical for debugging potential performance bottlenecks or memory issues. I'll need to trace the calls through `vivid`’s driver code to get a clear picture.
|
| 11/2 |
2026/07/17 00:44 |
tool |
grepper |
0m
Args: map[Expression:\.bytesperline PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-vid-cap.c=535=int vivid_g_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-554- for (p = 0; p < mp->num_planes; p++) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c:555: mp->plane_fmt[p].bytesperline = tpg_g_bytesperline(&dev->tpg, p);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-556- mp->plane_fmt[p].sizeimage =
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=564=int vivid_try_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-633-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:634: if (pfmt[p].bytesperline > max_bpl)
drivers/media/test-drivers/vivid/vivid-vid-cap.c:635: pfmt[p].bytesperline = max_bpl;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:636: if (pfmt[p].bytesperline < bytesperline)
drivers/media/test-drivers/vivid/vivid-vid-cap.c:637: pfmt[p].bytesperline = bytesperline;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-638-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:639: pfmt[p].sizeimage = (pfmt[p].bytesperline * mp->height) /
drivers/media/test-drivers/vivid/vivid-vid-cap.c-640- fmt->vdownsampling[p] + fmt->data_offset[p];
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-644- for (p = fmt->buffers; p < fmt->planes; p++)
drivers/media/test-drivers/vivid/vivid-vid-cap.c:645: pfmt[0].sizeimage += (pfmt[0].bytesperline * mp->height *
drivers/media/test-drivers/vivid/vivid-vid-cap.c-646- (fmt->bit_depth[p] / fmt->vdownsampling[p])) /
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=677=int vivid_s_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-788- for (p = 0; p < tpg_g_buffers(&dev->tpg); p++)
drivers/media/test-drivers/vivid/vivid-vid-cap.c:789: tpg_s_bytesperline(&dev->tpg, p, mp->plane_fmt[p].bytesperline);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-790- dev->field_cap = mp->field;
--
drivers/media/test-drivers/vivid/vivid-vid-out.c=317=int vivid_g_fmt_vid_out(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-334- for (p = 0; p < mp->num_planes; p++) {
drivers/media/test-drivers/vivid/vivid-vid-out.c:335: mp->plane_fmt[p].bytesperline = dev->bytesperline_out[p];
drivers/media/test-drivers/vivid/vivid-vid-out.c-336- mp->plane_fmt[p].sizeimage =
drivers/media/test-drivers/vivid/vivid-vid-out.c:337: mp->plane_fmt[p].bytesperline * mp->height /
drivers/media/test-drivers/vivid/vivid-vid-out.c-338- fmt->vdownsampling[p] + fmt->data_offset[p];
--
drivers/media/test-drivers/vivid/vivid-vid-out.c=349=int vivid_try_fmt_vid_out(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-409-
drivers/media/test-drivers/vivid/vivid-vid-out.c:410: if (pfmt[p].bytesperline > max_bpl)
drivers/media/test-drivers/vivid/vivid-vid-out.c:411: pfmt[p].bytesperline = max_bpl;
drivers/media/test-drivers/vivid/vivid-vid-out.c:412: if (pfmt[p].bytesperline < bytesperline)
drivers/media/test-drivers/vivid/vivid-vid-out.c:413: pfmt[p].bytesperline = bytesperline;
drivers/media/test-drivers/vivid/vivid-vid-out.c-414-
drivers/media/test-drivers/vivid/vivid-vid-out.c:415: pfmt[p].sizeimage = (pfmt[p].bytesperline * mp->height) /
drivers/media/test-drivers/vivid/vivid-vid-out.c-416- fmt->vdownsampling[p] + fmt->data_offset[p];
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-420- for (p = fmt->buffers; p < fmt->planes; p++)
drivers/media/test-drivers/vivid/vivid-vid-out.c:421: pfmt[0].sizeimage += (pfmt[0].bytesperline * mp->height *
drivers/media/test-drivers/vivid/vivid-vid-out.c-422- (fmt->bit_depth[p] / fmt->vdownsampling[p])) /
--
drivers/media/test-drivers/vivid/vivid-vid-out.c=447=int vivid_s_fmt_vid_out(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-553- for (p = 0; p < mp->num_planes; p++)
drivers/media/test-drivers/vivid/vivid-vid-out.c:554: dev->bytesperline_out[p] = mp->plane_fmt[p].bytesperline;
drivers/media/test-drivers/vivid/vivid-vid-out.c-555- for (p = dev->fmt_out->buffers; p < dev->fmt_out->planes; p++)
--
drivers/media/test-drivers/vivid/vivid-vid-out.c=902=int vivid_vid_out_g_fbuf(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-920- a->fmt.pixelformat = V4L2_PIX_FMT_RGB565;
drivers/media/test-drivers/vivid/vivid-vid-out.c:921: a->fmt.bytesperline = dev->display_byte_stride;
drivers/media/test-drivers/vivid/vivid-vid-out.c:922: a->fmt.sizeimage = a->fmt.height * a->fmt.bytesperline;
drivers/media/test-drivers/vivid/vivid-vid-out.c-923- a->fmt.field = V4L2_FIELD_NONE;
]
|
| 12/2 |
2026/07/17 00:44 |
llm |
expert |
0m
Model:
Tokens:
input: 14186
output: 54
thoughts: 342
Thoughts: **Analyzing the Potential Vulnerability in the Vivid V4L2 Driver**
Okay, so the `vivid` driver... right, it's a *test* driver for V4L2. Not actual hardware. Interesting. The immediate question is access control. Can an unprivileged user even *access* this thing? Normally, `/dev/video*` nodes created by `vivid` would be in the `video` group, or accessible through ACLs. But `vivid` itself is a kernel module, and test drivers are typically *not* loaded by default.
Hang on, the bug report mentions `vivid-000-vid-c`. That suggests it *is* potentially loaded, or at least that's what's generating the crash. Is `vivid` even enabled in production kernels? Typically, `CONFIG_VIDEO_VIVID` is disabled or not autoloaded. Let's see... obviously `modprobe` requires root, so an unprivileged user can't load it. But, and this is the crux, *if* it's already loaded, could they trigger something? Right, if they have access to `/dev/videoX`. That's the key question: is this bug exploitable, and could it lead to a denial of service?
Okay, back to the bug report. Let's look at the vulnerable code: `tpg_fill_plane_pattern` does a `memcpy(vbuf, linestart_older, img_width);`. Now the critical point is `img_width` is set to 5120, but the buffer `vbuf` is only allocated with 4096 bytes. Now this is the heart of the issue: why is `img_width` larger than the buffer size? This means there is a buffer overflow. Let's dig deeper and look into `tpg_fill_plane_buffer` to figure out where the vulnerability lies.
|
| 13/2 |
2026/07/17 00:44 |
tool |
read-file |
0m
Args: map[File:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c FirstLine:2630 LineCount:50]
Results: map[Contents:2630: unsigned p, u8 *vbuf)
2631: {
2632: struct tpg_draw_params params;
2633: unsigned factor = V4L2_FIELD_HAS_T_OR_B(tpg->field) ? 2 : 1;
2634:
2635: /* Coarse scaling with Bresenham */
2636: unsigned int_part = (tpg->crop.height / factor) / tpg->compose.height;
2637: unsigned fract_part = (tpg->crop.height / factor) % tpg->compose.height;
2638: unsigned src_y = 0;
2639: unsigned error = 0;
2640: unsigned h;
2641:
2642: tpg_recalc(tpg);
2643:
2644: params.is_tv = std;
2645: params.is_60hz = std & V4L2_STD_525_60;
2646: params.twopixsize = tpg->twopixelsize[p];
2647: params.img_width = tpg_hdiv(tpg, p, tpg->compose.width);
2648: params.stride = tpg->bytesperline[p];
2649: params.hmax = (tpg->compose.height * tpg->perc_fill) / 100;
2650:
2651: tpg_fill_params_pattern(tpg, p, ¶ms);
2652: tpg_fill_params_extras(tpg, p, ¶ms);
2653:
2654: vbuf += tpg_hdiv(tpg, p, tpg->compose.left);
2655:
2656: for (h = 0; h < tpg->compose.height; h++) {
2657: unsigned buf_line;
2658:
2659: params.frame_line = tpg_calc_frameline(tpg, src_y, tpg->field);
2660: params.frame_line_next = params.frame_line;
2661: buf_line = tpg_calc_buffer_line(tpg, h, tpg->field);
2662: src_y += int_part;
2663: error += fract_part;
2664: if (error >= tpg->compose.height) {
2665: error -= tpg->compose.height;
2666: src_y++;
2667: }
2668:
2669: /*
2670: * For line-interleaved formats determine the 'plane'
2671: * based on the buffer line.
2672: */
2673: if (tpg_g_interleaved(tpg))
2674: p = tpg_g_interleaved_plane(tpg, buf_line);
2675:
2676: if (tpg->vdownsampling[p] > 1) {
2677: /*
2678: * When doing vertical downsampling the field setting
2679: * matters: for SEQ_BT/TB we downsample each field
]
|
| 14/2 |
2026/07/17 00:44 |
llm |
expert |
0m
Model:
Tokens:
input: 15877
output: 54
thoughts: 66
Thoughts: **Analyzing Image Width and Filling Patterns**
Okay, so I'm looking at this code and specifically, this line: `params.img_width = tpg_hdiv(tpg, p, tpg->compose.width);`. I see that `img_width` within the `params` struct is being calculated using `tpg_hdiv` and initialized with the result of that function, which takes several arguments. The most relevant argument here is `tpg->compose.width`. Seems straightforward – we're deriving the image width, potentially based on some kind of division operation. I need to keep that value in mind.
Now, the next thing that jumps out is that `tpg_fill_plane_pattern` is using that calculated `params.img_width` as `img_width`. So, the `img_width` we just determined is now a parameter that's passed into this `tpg_fill_plane_pattern` function. This makes me want to examine *that* function now because it will be important to understanding how this value is used in the image generation pipeline. Let's delve into what this `tpg_fill_plane_pattern` function is doing.
|
| 15/2 |
2026/07/17 00:44 |
tool |
read-file |
0m
Args: map[File:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c FirstLine:2570 LineCount:50]
Results: map[Contents:2570: break;
2571: case V4L2_FIELD_NONE:
2572: case V4L2_FIELD_TOP:
2573: case V4L2_FIELD_BOTTOM:
2574: case V4L2_FIELD_SEQ_BT:
2575: case V4L2_FIELD_SEQ_TB:
2576: avg_pat = tpg_pattern_avg(tpg, pat_line_old, pat_line_next_old);
2577: if (avg_pat >= 0)
2578: linestart_older = tpg->downsampled_lines[avg_pat][p] +
2579: mv_hor_old;
2580: avg_pat = tpg_pattern_avg(tpg, pat_line_new, pat_line_next_new);
2581: if (avg_pat >= 0)
2582: linestart_newer = tpg->downsampled_lines[avg_pat][p] +
2583: mv_hor_new;
2584: break;
2585: }
2586: }
2587: linestart_older += line_offset;
2588: linestart_newer += line_offset;
2589: }
2590: if (tpg->field_alternate) {
2591: linestart_top = linestart_bottom = linestart_older;
2592: } else if (params->is_60hz) {
2593: linestart_top = linestart_newer;
2594: linestart_bottom = linestart_older;
2595: } else {
2596: linestart_top = linestart_older;
2597: linestart_bottom = linestart_newer;
2598: }
2599:
2600: switch (tpg->field) {
2601: case V4L2_FIELD_INTERLACED:
2602: case V4L2_FIELD_INTERLACED_TB:
2603: case V4L2_FIELD_SEQ_TB:
2604: case V4L2_FIELD_SEQ_BT:
2605: if (even)
2606: memcpy(vbuf, linestart_top, img_width);
2607: else
2608: memcpy(vbuf, linestart_bottom, img_width);
2609: break;
2610: case V4L2_FIELD_INTERLACED_BT:
2611: if (even)
2612: memcpy(vbuf, linestart_bottom, img_width);
2613: else
2614: memcpy(vbuf, linestart_top, img_width);
2615: break;
2616: case V4L2_FIELD_TOP:
2617: memcpy(vbuf, linestart_top, img_width);
2618: break;
2619: case V4L2_FIELD_BOTTOM:
]
|
| 16/2 |
2026/07/17 00:44 |
llm |
expert |
0m
Model:
Tokens:
input: 17102
output: 47
thoughts: 50
Thoughts: Okay, here's my take on that.
**Analyzing the Image Buffer Size Issue**
Alright, so the core problem seems to be an incompatibility between the intended image width, which we're calling `img_width`, and the allocated buffer size. That buffer's been set up with a size derived from `pfmt[p].sizeimage`. The real question is: how is this `pfmt[p].sizeimage` value actually being calculated? This is where the root cause probably lies. I need to understand that calculation to trace where the discrepancy is occurring and determine how the allocated buffer is too small to accommodate the image data. Let's dig into that `pfmt[p].sizeimage` calculation.
|
| 17/2 |
2026/07/17 00:45 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-cap.c FirstLine:630 LineCount:50]
Results: map[Contents: 630: bytesperline = (mp->width * fmt->bit_depth[p]) >> 3;
631: /* Calculate the maximum supported bytesperline value */
632: max_bpl = (MAX_ZOOM * MAX_WIDTH * fmt->bit_depth[p]) >> 3;
633:
634: if (pfmt[p].bytesperline > max_bpl)
635: pfmt[p].bytesperline = max_bpl;
636: if (pfmt[p].bytesperline < bytesperline)
637: pfmt[p].bytesperline = bytesperline;
638:
639: pfmt[p].sizeimage = (pfmt[p].bytesperline * mp->height) /
640: fmt->vdownsampling[p] + fmt->data_offset[p];
641:
642: memset(pfmt[p].reserved, 0, sizeof(pfmt[p].reserved));
643: }
644: for (p = fmt->buffers; p < fmt->planes; p++)
645: pfmt[0].sizeimage += (pfmt[0].bytesperline * mp->height *
646: (fmt->bit_depth[p] / fmt->vdownsampling[p])) /
647: (fmt->bit_depth[0] / fmt->vdownsampling[0]);
648:
649: if (!user_set_csc || !v4l2_is_colorspace_valid(mp->colorspace))
650: mp->colorspace = vivid_colorspace_cap(dev);
651:
652: if (!user_set_csc || !v4l2_is_xfer_func_valid(mp->xfer_func))
653: mp->xfer_func = vivid_xfer_func_cap(dev);
654:
655: if (fmt->color_enc == TGP_COLOR_ENC_HSV) {
656: if (!user_set_csc || !v4l2_is_hsv_enc_valid(mp->hsv_enc))
657: mp->hsv_enc = vivid_hsv_enc_cap(dev);
658: } else if (fmt->color_enc == TGP_COLOR_ENC_YCBCR) {
659: if (!user_set_csc || !v4l2_is_ycbcr_enc_valid(mp->ycbcr_enc))
660: mp->ycbcr_enc = vivid_ycbcr_enc_cap(dev);
661: } else {
662: mp->ycbcr_enc = vivid_ycbcr_enc_cap(dev);
663: }
664:
665: if (fmt->color_enc == TGP_COLOR_ENC_YCBCR ||
666: fmt->color_enc == TGP_COLOR_ENC_RGB) {
667: if (!user_set_csc || !v4l2_is_quant_valid(mp->quantization))
668: mp->quantization = vivid_quantization_cap(dev);
669: } else {
670: mp->quantization = vivid_quantization_cap(dev);
671: }
672:
673: memset(mp->reserved, 0, sizeof(mp->reserved));
674: return 0;
675: }
676:
677: int vivid_s_fmt_vid_cap(struct file *file, void *priv,
678: struct v4l2_format *f)
679: {
]
|
| 18/2 |
2026/07/17 00:45 |
llm |
expert |
0m
Model:
Tokens:
input: 18362
output: 53
thoughts: 235
Thoughts: **Analyzing a Potential Buffer Overflow**
Okay, so I'm looking at this buffer size calculation: `pfmt[p].sizeimage = (pfmt[p].bytesperline * mp->height) / fmt->vdownsampling[p] + fmt->data_offset[p];`. Seems straightforward enough, but my expert eye is immediately drawn to the `mp->height` term. If that's small, `sizeimage` could also be small, which is a potential red flag.
The real trouble is with `tpg_fill_plane_buffer`, it writes `img_width` bytes per line. And `img_width` comes from `tpg_hdiv(tpg, p, tpg->compose.width)`. Right, `tpg->compose.width` is the *width* of the composition rectangle. My brain is already starting to piece together a dangerous scenario here. If that composition width is *larger* than `pfmt[p].bytesperline`, then `img_width` ends up being bigger than it should be, which means we can potentially write past the allocated buffer. A nasty out-of-bounds write is what I'm picturing.
But wait, I need to make sure I'm precise. Is `img_width` in bytes or pixels? I need to clarify that. Okay, it's calculated using `tpg_hdiv(tpg, p, tpg->compose.width)`. Time to dig into `tpg_hdiv` to fully understand what's happening. I need to know precisely how that width is being adjusted.
|
| 19/2 |
2026/07/17 00:45 |
tool |
read-file |
0m
Args: map[File:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c FirstLine:250 LineCount:50]
Results: map[Contents: 250: case V4L2_PIX_FMT_XRGB444:
251: case V4L2_PIX_FMT_ARGB444:
252: case V4L2_PIX_FMT_RGBX444:
253: case V4L2_PIX_FMT_RGBA444:
254: case V4L2_PIX_FMT_XBGR444:
255: case V4L2_PIX_FMT_ABGR444:
256: case V4L2_PIX_FMT_BGRX444:
257: case V4L2_PIX_FMT_BGRA444:
258: case V4L2_PIX_FMT_RGB555:
259: case V4L2_PIX_FMT_XRGB555:
260: case V4L2_PIX_FMT_ARGB555:
261: case V4L2_PIX_FMT_RGBX555:
262: case V4L2_PIX_FMT_RGBA555:
263: case V4L2_PIX_FMT_XBGR555:
264: case V4L2_PIX_FMT_ABGR555:
265: case V4L2_PIX_FMT_BGRX555:
266: case V4L2_PIX_FMT_BGRA555:
267: case V4L2_PIX_FMT_RGB555X:
268: case V4L2_PIX_FMT_XRGB555X:
269: case V4L2_PIX_FMT_ARGB555X:
270: case V4L2_PIX_FMT_BGR666:
271: case V4L2_PIX_FMT_RGB24:
272: case V4L2_PIX_FMT_BGR24:
273: case V4L2_PIX_FMT_RGB32:
274: case V4L2_PIX_FMT_BGR32:
275: case V4L2_PIX_FMT_XRGB32:
276: case V4L2_PIX_FMT_XBGR32:
277: case V4L2_PIX_FMT_ARGB32:
278: case V4L2_PIX_FMT_ABGR32:
279: case V4L2_PIX_FMT_RGBX32:
280: case V4L2_PIX_FMT_BGRX32:
281: case V4L2_PIX_FMT_RGBA32:
282: case V4L2_PIX_FMT_BGRA32:
283: tpg->color_enc = TGP_COLOR_ENC_RGB;
284: break;
285: case V4L2_PIX_FMT_GREY:
286: case V4L2_PIX_FMT_Y10:
287: case V4L2_PIX_FMT_Y12:
288: case V4L2_PIX_FMT_Y16:
289: case V4L2_PIX_FMT_Y16_BE:
290: case V4L2_PIX_FMT_Z16:
291: tpg->color_enc = TGP_COLOR_ENC_LUMA;
292: break;
293: case V4L2_PIX_FMT_YUV444:
294: case V4L2_PIX_FMT_YUV555:
295: case V4L2_PIX_FMT_YUV565:
296: case V4L2_PIX_FMT_YUV32:
297: case V4L2_PIX_FMT_AYUV32:
298: case V4L2_PIX_FMT_XYUV32:
299: case V4L2_PIX_FMT_VUYA32:
]
|
| 20/2 |
2026/07/17 00:45 |
llm |
expert |
0m
Model:
Tokens:
input: 20184
output: 39
thoughts: 13
Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and written in the first person:
**Finding the Missing Piece: `tpg_hdiv`**
Alright, I'm in the thick of this. The analysis is flowing, the model is humming, but there's a critical piece missing. Something feels…incomplete. The pieces are all in place, I think I'm *almost* there, but I can't quite get to the logical conclusion because I *need* `tpg_hdiv`. It’s like trying to assemble a complex mechanism without a key component. I’m pausing, taking a mental inventory. What am I missing? What is the core calculation? Is `tpg_hdiv` a variable? A function? A dataset? I need to track down this element. Is it something I've mislabeled? Or perhaps it isn't loaded correctly. Where does it exist in the flow? I need to locate it immediately. Otherwise, I will get stuck. I have to find it, understand its role, and ensure it's properly integrated into the workflow. Until that happens, I am stalled.
|
| 21/2 |
2026/07/17 00:45 |
tool |
grepper |
0m
Args: map[Expression:tpg_hdiv PathPrefix:drivers/media/common/v4l2-tpg/]
Results: map[Output:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1790=static void tpg_precalculate_line(struct tpg_data *tpg)
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1849- unsigned hdiv = tpg->hdownsampling[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1850: u8 *pos = tpg->lines[pat][p] + tpg_hdiv(tpg, p, x);
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1851-
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1863- for (p = 1; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1864: unsigned w = tpg_hdiv(tpg, p, tpg->scaled_width * 2);
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1865- u8 *pos1 = tpg->lines[pat][p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=2349=static void tpg_fill_plane_extras(const struct tpg_data *tpg,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2416- if (tpg->insert_sav) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2417: unsigned offset = tpg_hdiv(tpg, p, tpg->compose.width / 3);
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2418- u8 *p = vbuf + offset;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2431- if (tpg->insert_eav) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2432: unsigned offset = tpg_hdiv(tpg, p, tpg->compose.width * 2 / 3);
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2433- u8 *p = vbuf + offset;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=2629=void tpg_fill_plane_buffer(struct tpg_data *tpg, v4l2_std_id std,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2646- params.twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2647: params.img_width = tpg_hdiv(tpg, p, tpg->compose.width);
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2648- params.stride = tpg->bytesperline[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2653-
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2654: vbuf += tpg_hdiv(tpg, p, tpg->compose.left);
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2655-
]
|
| 22/2 |
2026/07/17 00:45 |
llm |
expert |
0m
Model:
Tokens:
input: 21531
output: 40
thoughts: 14
Thoughts: Here's my thought process, summarized as you requested:
**Deconstructing "tpg_hdiv"**
Okay, so I'm encountering "tpg_hdiv," and the first thing I need to do is pinpoint its meaning. It's crucial to understand the foundation. Let's start with a thorough definition search. I need to know exactly what this term represents. Is it an acronym? A specialized term in a particular domain? Or perhaps a newly coined phrase? The level of analysis required will depend on its complexity and origin, so getting the definition from the source is step one. Once I understand the definition, I can start to engage with this concept.
|
| 23/2 |
2026/07/17 00:46 |
tool |
grepper |
0m
Error:
Args: map[Expression:define tpg_hdiv PathPrefix:drivers/media/common/v4l2-tpg/]
Results:
|
| 24/2 |
2026/07/17 00:46 |
llm |
expert |
0m
Model:
Tokens:
input: 21740
output: 29
thoughts: 11
Thoughts: Okay, here's my interpretation of that thought process, tailored for an expert audience, and presented as if it were my own internal monologue:
**Investigating a Potentially Hidden Implementation**
Hmm, let me see... I'm looking at this piece of code, and something about how this function behaves is nagging at me. It's concise, it’s acting like it is returning values based on it's current context. Could this be some sort of inline function defined right there in the header file? That's the most likely explanation given its performance characteristics. I’m going to need to look into the header declarations to confirm this suspicion, and see how this specific function is defined. It would explain the observed behavior.
|
| 25/2 |
2026/07/17 00:46 |
tool |
grepper |
0m
Args: map[Expression:tpg_hdiv PathPrefix:include/media/]
Results: map[Output:include/media/tpg/v4l2-tpg.h=434=static inline unsigned tpg_g_twopixelsize(const struct tpg_data *tpg, unsigned plane)
--
include/media/tpg/v4l2-tpg.h-438-
include/media/tpg/v4l2-tpg.h:439:static inline unsigned tpg_hdiv(const struct tpg_data *tpg,
include/media/tpg/v4l2-tpg.h-440- unsigned plane, unsigned x)
--
include/media/tpg/v4l2-tpg.h=451=static inline unsigned tpg_hscale_div(const struct tpg_data *tpg,
--
include/media/tpg/v4l2-tpg.h-453-{
include/media/tpg/v4l2-tpg.h:454: return tpg_hdiv(tpg, plane, tpg_hscale(tpg, x));
include/media/tpg/v4l2-tpg.h-455-}
]
|
| 26/2 |
2026/07/17 00:46 |
llm |
expert |
0m
Model:
Tokens:
input: 22224
output: 44
thoughts: 29
Thoughts: Okay, let's dive into this. Here's my take on those lines of code, presented as a summary of my immediate thought process:
**Diving into `v4l2-tpg.h`**
Alright, I'm heading over to `include/media/tpg/v4l2-tpg.h` and specifically around line 439. That usually means there's something interesting happening there. I anticipate it deals with the V4L2 Test Pattern Generator (TPG), which means likely configuring or handling a particular test pattern setup. Line 439 is likely where we're going to see the core structures, functions, or macros involved in handling a specific parameter. Hopefully it's not too dense, and is well-commented. I'm really curious to see what context it's providing in this section.
|
| 27/2 |
2026/07/17 00:46 |
tool |
read-file |
0m
Args: map[File:include/media/tpg/v4l2-tpg.h FirstLine:430 LineCount:20]
Results: map[Contents: 430: {
431: return tpg->interleaved;
432: }
433:
434: static inline unsigned tpg_g_twopixelsize(const struct tpg_data *tpg, unsigned plane)
435: {
436: return tpg->twopixelsize[plane];
437: }
438:
439: static inline unsigned tpg_hdiv(const struct tpg_data *tpg,
440: unsigned plane, unsigned x)
441: {
442: return ((x / tpg->hdownsampling[plane]) & tpg->hmask[plane]) *
443: tpg->twopixelsize[plane] / 2;
444: }
445:
446: static inline unsigned tpg_hscale(const struct tpg_data *tpg, unsigned x)
447: {
448: return (x * tpg->scaled_width) / tpg->src_width;
449: }
]
|
| 28/2 |
2026/07/17 00:46 |
llm |
expert |
0m
Model:
Tokens:
input: 22791
output: 47
thoughts: 155
Thoughts: **Decoding the Image Buffer Allocation**
Okay, let's break this down. It seems like I'm trying to figure out how this image buffer is allocated, specifically how the bytes-per-line calculation interacts with the overall image size. I see `tpg_hdiv` being used to compute `img_width` based on `tpg->compose.width`, effectively the number of bytes for a given number of pixels. This `img_width` should represent the bytes per line of the composed image, that seems straightforward enough.
However, the actual buffer allocation seems to rely on `pfmt[p].sizeimage`. Hmm, and that's where things get interesting. `sizeimage` is calculated from a combination of `bytesperline`, the height, and downsampling factors. And wait a second, I see `bytesperline` itself hinges on `mp->width`, but this `mp->width` isn't necessarily the same as the "composed" width I saw earlier. This feels like an area ripe for a potential miscalculation. Is it using the width from the input format (which might be different after processing)? This discrepancy is where I need to focus.
I need to confirm if this width calculation accounts for any downsampling. I'm going to look into `vivid_try_fmt_vid_cap` to see how those calculations are linked, to ensure there aren't any logical inconsistencies with the downsampling.
|
| 29/2 |
2026/07/17 00:46 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-cap.c FirstLine:610 LineCount:50]
Results: map[Contents: 610: v4l2_rect_set_min_size(&r, &vivid_min_rect);
611: v4l2_rect_set_max_size(&r, &vivid_max_rect);
612: if (dev->has_scaler_cap && !dev->has_compose_cap) {
613: struct v4l2_rect max_r = { 0, 0, MAX_ZOOM * w, MAX_ZOOM * h };
614:
615: v4l2_rect_set_max_size(&r, &max_r);
616: } else if (!dev->has_scaler_cap && dev->has_crop_cap && !dev->has_compose_cap) {
617: v4l2_rect_set_max_size(&r, &dev->src_rect);
618: } else if (!dev->has_scaler_cap && !dev->has_crop_cap) {
619: v4l2_rect_set_min_size(&r, &dev->src_rect);
620: }
621: mp->width = r.width;
622: mp->height = r.height / factor;
623: }
624:
625: /* This driver supports custom bytesperline values */
626:
627: mp->num_planes = fmt->buffers;
628: for (p = 0; p < fmt->buffers; p++) {
629: /* Calculate the minimum supported bytesperline value */
630: bytesperline = (mp->width * fmt->bit_depth[p]) >> 3;
631: /* Calculate the maximum supported bytesperline value */
632: max_bpl = (MAX_ZOOM * MAX_WIDTH * fmt->bit_depth[p]) >> 3;
633:
634: if (pfmt[p].bytesperline > max_bpl)
635: pfmt[p].bytesperline = max_bpl;
636: if (pfmt[p].bytesperline < bytesperline)
637: pfmt[p].bytesperline = bytesperline;
638:
639: pfmt[p].sizeimage = (pfmt[p].bytesperline * mp->height) /
640: fmt->vdownsampling[p] + fmt->data_offset[p];
641:
642: memset(pfmt[p].reserved, 0, sizeof(pfmt[p].reserved));
643: }
644: for (p = fmt->buffers; p < fmt->planes; p++)
645: pfmt[0].sizeimage += (pfmt[0].bytesperline * mp->height *
646: (fmt->bit_depth[p] / fmt->vdownsampling[p])) /
647: (fmt->bit_depth[0] / fmt->vdownsampling[0]);
648:
649: if (!user_set_csc || !v4l2_is_colorspace_valid(mp->colorspace))
650: mp->colorspace = vivid_colorspace_cap(dev);
651:
652: if (!user_set_csc || !v4l2_is_xfer_func_valid(mp->xfer_func))
653: mp->xfer_func = vivid_xfer_func_cap(dev);
654:
655: if (fmt->color_enc == TGP_COLOR_ENC_HSV) {
656: if (!user_set_csc || !v4l2_is_hsv_enc_valid(mp->hsv_enc))
657: mp->hsv_enc = vivid_hsv_enc_cap(dev);
658: } else if (fmt->color_enc == TGP_COLOR_ENC_YCBCR) {
659: if (!user_set_csc || !v4l2_is_ycbcr_enc_valid(mp->ycbcr_enc))
]
|
| 30/2 |
2026/07/17 00:46 |
llm |
expert |
0m
Model:
Tokens:
input: 24401
output: 40
thoughts: 80
Thoughts: Okay, let's break this down.
**Understanding Line Width and Image Composition**
Right, so `mp->width` is essentially setting the *floor* for how many bytes we need per line. That makes sense. But if `tpg->compose.width` is actually bigger than that minimum width, then the image width (`img_width`) isn't necessarily bound by the minimum bytes per line. That opens up some interesting possibilities.
The key question then becomes: Is `tpg->compose.width` *in fact* larger than `mp->width`? I need to know under what conditions this is true, because that dictates how we manage memory allocation and image layout. Time to dig into where `tpg->compose` is being set and how its width is determined relative to `mp->width`. I need to trace back the assignments to confirm the relationship and its implications. This will be critical for avoiding potential buffer overflows or unexpected image cropping. Let's start the investigation.
|
| 31/2 |
2026/07/17 00:46 |
tool |
grepper |
0m
Args: map[Expression:compose PathPrefix:drivers/media/test-drivers/vivid/vivid-vid-cap.c]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-vid-cap.c=389=void vivid_update_format_cap(struct vivid_dev *dev, bool keep_controls)
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-455- dev->crop_bounds_cap = dev->src_rect;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:456: dev->compose_cap = dev->crop_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-457- if (V4L2_FIELD_HAS_T_OR_B(dev->field_cap))
drivers/media/test-drivers/vivid/vivid-vid-cap.c:458: dev->compose_cap.height /= 2;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:459: dev->fmt_cap_rect = dev->compose_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-460- tpg_s_video_aspect(&dev->tpg, vivid_get_video_aspect(dev));
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=564=int vivid_try_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-603- if (vivid_is_webcam(dev) ||
drivers/media/test-drivers/vivid/vivid-vid-cap.c:604: (!dev->has_scaler_cap && !dev->has_crop_cap && !dev->has_compose_cap)) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-605- mp->width = w;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-611- v4l2_rect_set_max_size(&r, &vivid_max_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:612: if (dev->has_scaler_cap && !dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-613- struct v4l2_rect max_r = { 0, 0, MAX_ZOOM * w, MAX_ZOOM * h };
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-615- v4l2_rect_set_max_size(&r, &max_r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:616: } else if (!dev->has_scaler_cap && dev->has_crop_cap && !dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-617- v4l2_rect_set_max_size(&r, &dev->src_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=677=int vivid_s_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-682- struct v4l2_rect *crop = &dev->crop_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:683: struct v4l2_rect *compose = &dev->compose_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-684- struct vb2_queue *q = &dev->vb_vid_cap_q;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-704- if (!vivid_is_webcam(dev) &&
drivers/media/test-drivers/vivid/vivid-vid-cap.c:705: (dev->has_scaler_cap || dev->has_crop_cap || dev->has_compose_cap)) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-706- struct v4l2_rect r = { 0, 0, mp->width, mp->height };
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-708- if (dev->has_scaler_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c:709: if (dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c:710: v4l2_rect_map_inside(compose, &r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-711- else
drivers/media/test-drivers/vivid/vivid-vid-cap.c:712: *compose = r;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:713: if (dev->has_crop_cap && !dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-714- struct v4l2_rect min_r = {
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-730- 0, 0,
drivers/media/test-drivers/vivid/vivid-vid-cap.c:731: compose->width / MAX_ZOOM,
drivers/media/test-drivers/vivid/vivid-vid-cap.c:732: factor * compose->height / MAX_ZOOM
drivers/media/test-drivers/vivid/vivid-vid-cap.c-733- };
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-735- 0, 0,
drivers/media/test-drivers/vivid/vivid-vid-cap.c:736: compose->width * MAX_ZOOM,
drivers/media/test-drivers/vivid/vivid-vid-cap.c:737: factor * compose->height * MAX_ZOOM
drivers/media/test-drivers/vivid/vivid-vid-cap.c-738- };
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-743- }
drivers/media/test-drivers/vivid/vivid-vid-cap.c:744: } else if (dev->has_crop_cap && !dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-745- r.height *= factor;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-749- r.height /= factor;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:750: v4l2_rect_set_size_to(compose, &r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-751- } else if (!dev->has_crop_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c:752: v4l2_rect_map_inside(compose, &r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-753- } else {
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-756- v4l2_rect_map_inside(crop, &dev->crop_bounds_cap);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:757: compose->top *= factor;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:758: compose->height *= factor;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:759: v4l2_rect_set_size_to(compose, crop);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:760: v4l2_rect_map_inside(compose, &r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:761: compose->top /= factor;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:762: compose->height /= factor;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-763- }
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-778-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:779: v4l2_rect_set_size_to(compose, &r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-780- r.height *= factor;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-794- tpg_s_field(&dev->tpg, dev->field_cap, false);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:795: tpg_s_crop_compose(&dev->tpg, &dev->crop_cap, &dev->compose_cap);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-796- if (vivid_is_sdtv_cap(dev))
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=870=int vivid_vid_cap_g_selection(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-874-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:875: if (!dev->has_crop_cap && !dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-876- return -ENOTTY;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-895- case V4L2_SEL_TGT_COMPOSE_BOUNDS:
drivers/media/test-drivers/vivid/vivid-vid-cap.c:896: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-897- return -EINVAL;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-900- case V4L2_SEL_TGT_COMPOSE:
drivers/media/test-drivers/vivid/vivid-vid-cap.c:901: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-902- return -EINVAL;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:903: sel->r = dev->compose_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-904- break;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-905- case V4L2_SEL_TGT_COMPOSE_DEFAULT:
drivers/media/test-drivers/vivid/vivid-vid-cap.c:906: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-907- return -EINVAL;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=916=int vivid_vid_cap_s_selection(struct file *file, void *priv, struct v4l2_selection *s)
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-919- struct v4l2_rect *crop = &dev->crop_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:920: struct v4l2_rect *compose = &dev->compose_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-921- unsigned factor = V4L2_FIELD_HAS_T_OR_B(dev->field_cap) ? 2 : 1;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-923-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:924: if (!dev->has_crop_cap && !dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-925- return -ENOTTY;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-956- v4l2_rect_set_min_size(&fmt, &min_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:957: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-958- v4l2_rect_set_max_size(&fmt, &max_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-961- return -EBUSY;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:962: if (dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c:963: v4l2_rect_set_min_size(compose, &min_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:964: v4l2_rect_set_max_size(compose, &max_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-965- }
drivers/media/test-drivers/vivid/vivid-vid-cap.c:966: v4l2_rect_map_inside(compose, &fmt);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-967- dev->fmt_cap_rect = fmt;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-968- tpg_s_buf_height(&dev->tpg, fmt.height);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:969: } else if (dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-970- struct v4l2_rect fmt = dev->fmt_cap_rect;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-977- tpg_s_buf_height(&dev->tpg, fmt.height);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:978: v4l2_rect_set_size_to(compose, &s->r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:979: v4l2_rect_map_inside(compose, &dev->fmt_cap_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-980- } else {
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-984- v4l2_rect_set_size_to(&dev->fmt_cap_rect, &s->r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:985: v4l2_rect_set_size_to(compose, &s->r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:986: v4l2_rect_map_inside(compose, &dev->fmt_cap_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-987- tpg_s_buf_height(&dev->tpg, dev->fmt_cap_rect.height);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-993- case V4L2_SEL_TGT_COMPOSE:
drivers/media/test-drivers/vivid/vivid-vid-cap.c:994: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-995- return -EINVAL;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1037- v4l2_rect_map_inside(&s->r, &dev->fmt_cap_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:1038: *compose = s->r;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1039- break;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1043-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:1044: tpg_s_crop_compose(&dev->tpg, crop, compose);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1045- return 0;
]
|
| 32/2 |
2026/07/17 00:46 |
llm |
expert |
0m
Model:
Tokens:
input: 29274
output: 38
thoughts: 565
Thoughts: **Analyzing the Capture Rectangle and Image Width Logic**
Okay, so I'm looking at how this `vivid_vid_cap_s_selection` function interacts with the capture process. It seems that `compose_cap` within `vivid_vid_cap_s_selection` directly influences `tpg->compose`'s dimensions. If `compose_cap` is set to a seemingly large value, I'd expect `tpg->compose.width` to become equally large. However, there's a crucial check with `v4l2_rect_map_inside(&s->r, &dev->fmt_cap_rect);`. This ensures `tpg->compose` stays within the bounds defined by `dev->fmt_cap_rect`, which itself gets updated when the format is set. That's good, prevents runaway values.
But hold on, let's back up and check how `compose` is handled in `vivid_s_fmt_vid_cap`. I see a conditional here: if the device supports a scaler, and has a compose capability, it uses `v4l2_rect_map_inside` again to keep `compose` constrained by a rectangle `r`, otherwise, `compose = r`. And this `r` is being initialized to the size of the media's resolution, represented by `{ 0, 0, mp->width, mp->height }`. So `compose` (and subsequently `tpg->compose`) is *always* mapped inside this media's dimensions, which means `tpg->compose.width` is inherently limited to be less than or equal to `mp->width`.
Then, we calculate `img_width` using `tpg_hdiv(tpg, p, tpg->compose.width)`. The function itself is proportional to `x`, so `img_width` should then be less than or equal to `tpg_hdiv(tpg, p, mp->width)`. This makes sense in keeping sizes within a bound. But, I'm now comparing this to `pfmt[p].bytesperline`, which is at least `(mp->width * fmt->bit_depth[p]) >> 3`. So, I'm wondering what is the relationship between the `img_width` and the actual bytes per line for the format?
Now, the core of the question: can `tpg_hdiv(tpg, p, mp->width)` actually result in a larger value than `(mp->width * fmt->bit_depth[p]) >> 3`? Let's dissect `tpg_hdiv` itself:
```c
static inline unsigned tpg_hdiv(const struct tpg_data *tpg,
unsigned plane, unsigned x)
{
return ((x / tpg->hdownsampling[plane]) & tpg->hmask[plane]) *
tpg->twopixelsize[plane] / 2;
}
```
Okay, the crucial part is `tpg->twopixelsize[plane] / 2`. This represents the number of bytes per pixel. So the key question is whether this bytes per pixel value can be larger than `fmt->bit_depth[p] >> 3` (which is also bytes per pixel). If `tpg->twopixelsize[plane]` is larger than `fmt->bit_depth[p]` (in bits) we have a problem. I need to understand how `twopixelsize` is derived to determine if this discrepancy is possible.
|
| 33/2 |
2026/07/17 00:47 |
tool |
grepper |
0m
Args: map[Expression:twopixelsize PathPrefix:drivers/media/common/v4l2-tpg/]
Results: map[Output:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=211=bool tpg_s_fourcc(struct tpg_data *tpg, u32 fourcc)
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-388- case V4L2_PIX_FMT_RGB332:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:389: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-390- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-425- case V4L2_PIX_FMT_Z16:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:426: tpg->twopixelsize[0] = 2 * 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-427- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-430- case V4L2_PIX_FMT_HSV24:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:431: tpg->twopixelsize[0] = 2 * 3;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-432- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-451- case V4L2_PIX_FMT_HSV32:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:452: tpg->twopixelsize[0] = 2 * 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-453- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-465- case V4L2_PIX_FMT_SRGGB8:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:466: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:467: tpg->twopixelsize[1] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-468- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-480- case V4L2_PIX_FMT_SBGGR16:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:481: tpg->twopixelsize[0] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:482: tpg->twopixelsize[1] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-483- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-492- case V4L2_PIX_FMT_YVU420M:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:493: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:494: tpg->twopixelsize[1] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:495: tpg->twopixelsize[2] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-496- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-498- case V4L2_PIX_FMT_NV42:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:499: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:500: tpg->twopixelsize[1] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-501- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=523=void tpg_reset_source(struct tpg_data *tpg, unsigned width, unsigned height,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-541- for (p = 0; p < tpg->planes; p++)
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:542: tpg->bytesperline[p] = (width * tpg->twopixelsize[p]) /
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-543- (2 * tpg->hdownsampling[p]);
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1133=static void gen_twopix(struct tpg_data *tpg,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1135-{
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1136: unsigned offset = odd * tpg->twopixelsize[0] / 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1137- u8 alpha = tpg->alpha_component;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1790=static void tpg_precalculate_line(struct tpg_data *tpg)
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1847- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1848: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1849- unsigned hdiv = tpg->hdownsampling[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1877- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1878: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1879- u8 *pos = tpg->contrast_line[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1887- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1888: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1889- u8 *pos = tpg->black_line[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1898- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1899: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1900- u8 *pos = tpg->random_line[p] + x * twopixsize / 2;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1997=void tpg_gen_text(const struct tpg_data *tpg, u8 *basep[TPG_MAX_PLANES][2],
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2029- /* Print text */
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2030: switch (tpg->twopixelsize[p]) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2031- case 2:
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=2629=void tpg_fill_plane_buffer(struct tpg_data *tpg, v4l2_std_id std,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2645- params.is_60hz = std & V4L2_STD_525_60;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2646: params.twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2647- params.img_width = tpg_hdiv(tpg, p, tpg->compose.width);
]
|
| 34/2 |
2026/07/17 00:47 |
llm |
expert |
0m
Model:
Tokens:
input: 33458
output: 35
thoughts: 466
Thoughts: **Analyzing Pixel Size Calculations and Potential Width Discrepancies**
Okay, let's break this down. `tpg->twopixelsize[p]` gives us the size of two pixels in bytes. Dividing that by two, `tpg->twopixelsize[p] / 2`, clearly yields the size of a single pixel in bytes, as expected. Now, in the `vivid_try_fmt_vid_cap` function, we calculate `bytesperline` using `(mp->width * fmt->bit_depth[p]) >> 3`. And, `fmt->bit_depth[p] >> 3` *also* calculates the bytes per pixel, just expressed differently, it's the same thing. This makes `bytesperline` equal to `mp->width * bytes_per_pixel`. We also know `img_width` is `tpg->compose.width * bytes_per_pixel`.
The potential issue is highlighted when `tpg->compose.width` is greater than `mp->width`, because that implies that the total bytes per line, `img_width` is greater than the calculated bytes per line, `bytesperline`. But, the `compose` struct is mapped inside `fmt_cap_rect`, which has the width of `mp->width`. So, the `compose` width should never exceed the capture width.
However, a potential race condition occurs because `vivid_vid_cap_s_selection` modifies `dev->compose_cap`. Specifically, `v4l2_rect_map_inside` ensures `compose` fits inside `dev->fmt_cap_rect`, which has the same width as `mp->width`. Therefore, `tpg->compose.width` is limited to be less than or equal to `mp->width`. So, *why* is `img_width` showing as 5120?
I need to double-check the maximum width parameters. Let me go look at `MAX_WIDTH` and `MAX_ZOOM` to make sure there's not something going on there that's overriding things.
|
| 35/2 |
2026/07/17 00:47 |
tool |
grepper |
0m
Args: map[Expression:define MAX_WIDTH PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-core.h-33-/* The maximum image width/height are set to 4K DMT */
drivers/media/test-drivers/vivid/vivid-core.h:34:#define MAX_WIDTH 4096
drivers/media/test-drivers/vivid/vivid-core.h-35-#define MAX_HEIGHT 2160
]
|
| 36/2 |
2026/07/17 00:47 |
llm |
expert |
0m
Model:
Tokens:
input: 34526
output: 47
thoughts: 431
Thoughts: **Investigating a Potential Buffer Overflow**
Okay, so I'm looking at this code and trying to figure out a possible buffer overflow. The initial setup has `MAX_WIDTH` at 4096 and `MAX_ZOOM` at 8. My immediate thought is, if the image width, `img_width`, can be 5120, that's already raising a red flag. We know that if `tpg->compose.width` is limited to 4096, and assuming a maximum of 4 bytes per pixel (like ARGB32), the theoretical maximum `img_width` could actually be 16384. But then, why is the buffer size only 4096?
I'm seeing the buffer is allocated using `pfmt[p].sizeimage`. The relevant function, `vivid_try_fmt_vid_cap`, calculates `sizeimage` like this: `(pfmt[p].bytesperline * mp->height) / fmt->vdownsampling[p] + fmt->data_offset[p]`. Now, if `mp->height` is, say, extremely small (maybe 1), then `sizeimage` seems to simplify to `bytesperline`. But, if `bytesperline` is reported as 5120, the implication is that `sizeimage` becomes 5120 as well! That doesn't align with the allocation of only 4096 bytes.
Wait, the bug report...that's key. It says "Write of size 5120 at addr...". The address belongs to a vmalloc region. That indicates the buffer size is only one page: 4096 bytes. So the core of the problem seems to be that `bytesperline` is 5120, but the allocated buffer only holds 4096.
This doesn't make sense! How can `sizeimage` be calculated as 4096 if the calculation is actually giving the value 5120 to `bytesperline`?
Hold on... I need to check how `sizeimage` is actually *set*. Is the user providing this value? Let me look at `vivid_s_fmt_vid_cap` to understand what's happening.
|
| 37/2 |
2026/07/17 00:47 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-cap.c FirstLine:677 LineCount:50]
Results: map[Contents: 677: int vivid_s_fmt_vid_cap(struct file *file, void *priv,
678: struct v4l2_format *f)
679: {
680: struct v4l2_pix_format_mplane *mp = &f->fmt.pix_mp;
681: struct vivid_dev *dev = video_drvdata(file);
682: struct v4l2_rect *crop = &dev->crop_cap;
683: struct v4l2_rect *compose = &dev->compose_cap;
684: struct vb2_queue *q = &dev->vb_vid_cap_q;
685: int ret = vivid_try_fmt_vid_cap(file, priv, f);
686: unsigned factor = 1;
687: unsigned p;
688: unsigned i;
689:
690: if (ret < 0)
691: return ret;
692:
693: if (vb2_is_busy(q)) {
694: dprintk(dev, 1, "%s device busy\n", __func__);
695: return -EBUSY;
696: }
697:
698: dev->fmt_cap = vivid_get_format(dev, mp->pixelformat);
699: if (V4L2_FIELD_HAS_T_OR_B(mp->field))
700: factor = 2;
701:
702: /* Note: the webcam input doesn't support scaling, cropping or composing */
703:
704: if (!vivid_is_webcam(dev) &&
705: (dev->has_scaler_cap || dev->has_crop_cap || dev->has_compose_cap)) {
706: struct v4l2_rect r = { 0, 0, mp->width, mp->height };
707:
708: if (dev->has_scaler_cap) {
709: if (dev->has_compose_cap)
710: v4l2_rect_map_inside(compose, &r);
711: else
712: *compose = r;
713: if (dev->has_crop_cap && !dev->has_compose_cap) {
714: struct v4l2_rect min_r = {
715: 0, 0,
716: r.width / MAX_ZOOM,
717: factor * r.height / MAX_ZOOM
718: };
719: struct v4l2_rect max_r = {
720: 0, 0,
721: r.width * MAX_ZOOM,
722: factor * r.height * MAX_ZOOM
723: };
724:
725: v4l2_rect_set_min_size(crop, &min_r);
726: v4l2_rect_set_max_size(crop, &max_r);
]
|
| 38/2 |
2026/07/17 00:47 |
llm |
expert |
0m
Model:
Tokens:
input: 36370
output: 47
thoughts: 113
Thoughts: **Analyzing the Video Capture Format Negotiation**
Okay, first things first, it seems that `vivid_try_fmt_vid_cap` is the initial function called in this process. Its primary job is to set the `sizeimage` field within the video format structure, `pfmt[p]`. Now, the crucial question that springs to mind is this: the user can provide a `sizeimage` value during the format negotiation, but how does `vivid_try_fmt_vid_cap` handle that input?
The initial assumption is that `vivid_try_fmt_vid_cap` might just overwrite any user-provided value if it falls below the minimum required size. However, the scenario that I must address is: what if the user-supplied `sizeimage` is smaller than what `vivid_try_fmt_vid_cap` *calculates*? Does this scenario cause any problems? I need to review the code for `vivid_try_fmt_vid_cap` more closely to be certain.
|
| 39/2 |
2026/07/17 00:48 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-cap.c FirstLine:630 LineCount:20]
Results: map[Contents: 630: bytesperline = (mp->width * fmt->bit_depth[p]) >> 3;
631: /* Calculate the maximum supported bytesperline value */
632: max_bpl = (MAX_ZOOM * MAX_WIDTH * fmt->bit_depth[p]) >> 3;
633:
634: if (pfmt[p].bytesperline > max_bpl)
635: pfmt[p].bytesperline = max_bpl;
636: if (pfmt[p].bytesperline < bytesperline)
637: pfmt[p].bytesperline = bytesperline;
638:
639: pfmt[p].sizeimage = (pfmt[p].bytesperline * mp->height) /
640: fmt->vdownsampling[p] + fmt->data_offset[p];
641:
642: memset(pfmt[p].reserved, 0, sizeof(pfmt[p].reserved));
643: }
644: for (p = fmt->buffers; p < fmt->planes; p++)
645: pfmt[0].sizeimage += (pfmt[0].bytesperline * mp->height *
646: (fmt->bit_depth[p] / fmt->vdownsampling[p])) /
647: (fmt->bit_depth[0] / fmt->vdownsampling[0]);
648:
649: if (!user_set_csc || !v4l2_is_colorspace_valid(mp->colorspace))
]
|
| 40/2 |
2026/07/17 00:48 |
llm |
expert |
0m
Model:
Tokens:
input: 37181
output: 37
thoughts: 288
Thoughts: **Analyzing the Vivid Video Capture Format**
Okay, so looking at this `vivid_try_fmt_vid_cap` function, it's immediately apparent that it's unconditionally overwriting the `pfmt[p].sizeimage` field. That's the key. This means the calculated `sizeimage` is *exactly* `(bytesperline * mp->height) / vdownsampling + data_offset`. I need to remember that.
Now, I'm trying to wrap my head around this specific scenario. If `sizeimage` ends up being 4096 and `bytesperline` is 5120, wouldn't that mean `mp->height` *has* to be zero? But wait... if `mp->height` *is* zero, then `sizeimage` is also zero. That doesn't make sense. There has to be something I am missing.
Then I see this conditional within `vivid_try_fmt_vid_cap`:
```c
if (vivid_is_webcam(dev) ||
(!dev->has_scaler_cap && !dev->has_crop_cap && !dev->has_compose_cap)) {
mp->width = w;
mp->height = h;
} else {
struct v4l2_rect r = { 0, 0, mp->width, mp->height * factor };
v4l2_rect_set_min_size(&r, &vivid_min_rect);
v4l2_rect_set_max_size(&r, &vivid_max_rect);
```
Okay, so depending on if it's a webcam, or if there's no scaling, cropping, or compositing capability, the width and height are directly set. Otherwise, there's a rectangle calculation... So it looks like `mp->height` is being *modified* in this second block. That's likely where the issue is. I need to understand that rectangle and how it impacts `mp->height`. Let's check `vivid_min_rect`...
|
| 41/2 |
2026/07/17 00:48 |
tool |
grepper |
0m
Args: map[Expression:vivid_min_rect PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-core.c=212=char *vivid_ctrl_svid_to_output_strings[MAX_MENU_ITEMS + 1] = {
--
drivers/media/test-drivers/vivid/vivid-core.c-216-
drivers/media/test-drivers/vivid/vivid-core.c:217:const struct v4l2_rect vivid_min_rect = {
drivers/media/test-drivers/vivid/vivid-core.c-218- 0, 0, MIN_WIDTH, MIN_HEIGHT
--
drivers/media/test-drivers/vivid/vivid-core.h-74-
drivers/media/test-drivers/vivid/vivid-core.h:75:extern const struct v4l2_rect vivid_min_rect;
drivers/media/test-drivers/vivid/vivid-core.h-76-extern const struct v4l2_rect vivid_max_rect;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=564=int vivid_try_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-609-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:610: v4l2_rect_set_min_size(&r, &vivid_min_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-611- v4l2_rect_set_max_size(&r, &vivid_max_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=916=int vivid_vid_cap_s_selection(struct file *file, void *priv, struct v4l2_selection *s)
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-937- return ret;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:938: v4l2_rect_set_min_size(&s->r, &vivid_min_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-939- v4l2_rect_set_max_size(&s->r, &dev->src_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-998- return ret;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:999: v4l2_rect_set_min_size(&s->r, &vivid_min_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1000- v4l2_rect_set_max_size(&s->r, &dev->fmt_cap_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-out.c=349=int vivid_try_fmt_vid_out(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-385-
drivers/media/test-drivers/vivid/vivid-vid-out.c:386: v4l2_rect_set_min_size(&r, &vivid_min_rect);
drivers/media/test-drivers/vivid/vivid-vid-out.c-387- v4l2_rect_set_max_size(&r, &vivid_max_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-out.c=681=int vivid_vid_out_s_selection(struct file *file, void *priv, struct v4l2_selection *s)
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-700- return ret;
drivers/media/test-drivers/vivid/vivid-vid-out.c:701: v4l2_rect_set_min_size(&s->r, &vivid_min_rect);
drivers/media/test-drivers/vivid/vivid-vid-out.c-702- v4l2_rect_set_max_size(&s->r, &dev->fmt_out_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-747- return ret;
drivers/media/test-drivers/vivid/vivid-vid-out.c:748: v4l2_rect_set_min_size(&s->r, &vivid_min_rect);
drivers/media/test-drivers/vivid/vivid-vid-out.c-749- v4l2_rect_set_max_size(&s->r, &dev->sink_rect);
]
|
| 42/2 |
2026/07/17 00:48 |
llm |
expert |
0m
Model:
Tokens:
input: 39221
output: 35
thoughts: 15
Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience:
**Analyzing Minimum Dimension Constraints**
Alright, let's get down to brass tacks. My initial thought process is to immediately hone in on `MIN_WIDTH` and `MIN_HEIGHT`. I'm assuming these are critical parameters, likely representing the absolute minimum acceptable dimensions for whatever system or process we're dealing with. Knowing their values is fundamental to understanding any constraints we're operating under. Are we talking about UI elements, image processing, physical objects, or something else entirely? The context isn't spelled out, but these values immediately jump out as the bedrock dimensions we need to work with. I’m thinking, let's quickly review these and then we can start to assess our options. Understanding this minimum will inform the design decisions we must make.
|
| 43/2 |
2026/07/17 00:48 |
tool |
grepper |
0m
Args: map[Expression:define MIN_WIDTH PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-core.h-36-/* The minimum image width/height */
drivers/media/test-drivers/vivid/vivid-core.h:37:#define MIN_WIDTH 16
drivers/media/test-drivers/vivid/vivid-core.h-38-#define MIN_HEIGHT MIN_WIDTH
]
|
| 44/2 |
2026/07/17 00:48 |
llm |
expert |
0m
Model:
Tokens:
input: 39547
output: 37
thoughts: 547
Thoughts: **Analyzing Image Buffer Allocation and Dimensions**
Okay, so I'm looking at this image data structure, and I'm trying to wrap my head around the memory allocation and dimensions. Let's start with the basics: `MIN_WIDTH` and `MIN_HEIGHT` are both 16. If `mp->height` is also 16, and `bytesperline` is 16, I'd expect `sizeimage` to be 256 (16 * 16). But wait, `sizeimage` is *actually* 4096. Ah, right, `vb2_vmalloc_alloc` is involved, and that's going to round up to a page size. That explains it, `vmalloc` allocates in page sizes.
So, the reported `sizeimage` could be less than 4096, but the actual allocation with `vb2_vmalloc_alloc` will *always* be 4096 bytes. That makes sense. But then I see that `img_width` is 5120. How is that even possible? I know `img_width` is determined by `tpg_hdiv(tpg, p, tpg->compose.width)`.
If `tpg->compose.width` is large, then `img_width` will be large. But hold on, `compose` is mapped inside `dev->fmt_cap_rect`, which is also `mp->width`. So, `tpg->compose.width` has to be less than or equal to `mp->width`. That means `img_width` is bounded by `tpg_hdiv(tpg, p, mp->width)`. And, I know that `bytesperline` is at least `(mp->width * fmt->bit_depth[p]) >> 3`.
Now the question is, could `tpg_hdiv(tpg, p, mp->width)` be larger than the `(mp->width * fmt->bit_depth[p]) >> 3`? I need to go back and check the definition of `tpg_hdiv`:
```c
static inline unsigned tpg_hdiv(const struct tpg_data *tpg,
unsigned plane, unsigned x)
{
return ((x / tpg->hdownsampling[plane]) & tpg->hmask[plane]) *
tpg->twopixelsize[plane] / 2;
}
```
Okay, if `tpg->hdownsampling[plane]` is 1, and `tpg->hmask[plane]` is `~0`, that simplifies to `x * tpg->twopixelsize[plane] / 2`. The critical question then is whether `tpg->twopixelsize[plane] / 2` is larger than `fmt->bit_depth[p] >> 3`. I'll need to check the `vivid_get_format` function to see if that's possible, and how the format determines those values. I need to keep in mind, there are different *planes* to consider here, too.
|
| 45/2 |
2026/07/17 00:48 |
tool |
grepper |
0m
Args: map[Expression:vivid_get_format PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-vid-cap.c=564=int vivid_try_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-576-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:577: fmt = vivid_get_format(dev, mp->pixelformat);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-578- if (!fmt) {
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-581- mp->pixelformat = V4L2_PIX_FMT_YUYV;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:582: fmt = vivid_get_format(dev, mp->pixelformat);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-583- }
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=677=int vivid_s_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-697-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:698: dev->fmt_cap = vivid_get_format(dev, mp->pixelformat);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-699- if (V4L2_FIELD_HAS_T_OR_B(mp->field))
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=1655=int vidioc_enum_framesizes(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1661- return -EINVAL;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:1662: if (vivid_get_format(dev, fsize->pixel_format) == NULL)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1663- return -EINVAL;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=1684=int vidioc_enum_frameintervals(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1690-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:1691: fmt = vivid_get_format(dev, fival->pixel_format);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-1692- if (!fmt)
--
drivers/media/test-drivers/vivid/vivid-vid-common.c=34=struct vivid_fmt vivid_formats[] = {
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-756-
drivers/media/test-drivers/vivid/vivid-vid-common.c:757:const struct vivid_fmt *vivid_get_format(struct vivid_dev *dev, u32 pixelformat)
drivers/media/test-drivers/vivid/vivid-vid-common.c-758-{
--
drivers/media/test-drivers/vivid/vivid-vid-common.h=21=extern const struct v4l2_dv_timings_cap vivid_dv_timings_cap;
drivers/media/test-drivers/vivid/vivid-vid-common.h-22-
drivers/media/test-drivers/vivid/vivid-vid-common.h:23:const struct vivid_fmt *vivid_get_format(struct vivid_dev *dev, u32 pixelformat);
drivers/media/test-drivers/vivid/vivid-vid-common.h-24-
--
drivers/media/test-drivers/vivid/vivid-vid-out.c=349=int vivid_try_fmt_vid_out(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-361-
drivers/media/test-drivers/vivid/vivid-vid-out.c:362: fmt = vivid_get_format(dev, mp->pixelformat);
drivers/media/test-drivers/vivid/vivid-vid-out.c-363- if (!fmt) {
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-366- mp->pixelformat = V4L2_PIX_FMT_YUYV;
drivers/media/test-drivers/vivid/vivid-vid-out.c:367: fmt = vivid_get_format(dev, mp->pixelformat);
drivers/media/test-drivers/vivid/vivid-vid-out.c-368- }
--
drivers/media/test-drivers/vivid/vivid-vid-out.c=447=int vivid_s_fmt_vid_out(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-out.c-479-
drivers/media/test-drivers/vivid/vivid-vid-out.c:480: dev->fmt_out = vivid_get_format(dev, mp->pixelformat);
drivers/media/test-drivers/vivid/vivid-vid-out.c-481- if (V4L2_FIELD_HAS_T_OR_B(mp->field))
]
|
| 46/2 |
2026/07/17 00:48 |
llm |
expert |
0m
Model:
Tokens:
input: 42276
output: 46
thoughts: 33
Thoughts: Here's my analysis of the provided text, structured as a first-person expert summary:
**Diving into `vivid_formats`**
Okay, so we're talking about `vivid_formats`. Right away, my brain goes to "This is likely a key data structure for the VIVID test driver, likely defining the video formats it supports." The fact that it's in `drivers/media/test-drivers/vivid/vivid-vid-common.c` confirms this suspicion. My experience tells me this is the file where we'd expect the common, fundamental video format definitions for the virtual video device to reside. I'll need to know its structure and how it's used to understand the driver's capabilities and, potentially, its limitations regarding formats. This is the starting point for really digging into how the video device interacts with different capture and output pipelines.
|
| 47/2 |
2026/07/17 00:49 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-common.c FirstLine:34 LineCount:50]
Results: map[Contents: 34: struct vivid_fmt vivid_formats[] = {
35: {
36: .fourcc = V4L2_PIX_FMT_YUYV,
37: .vdownsampling = { 1 },
38: .bit_depth = { 16 },
39: .color_enc = TGP_COLOR_ENC_YCBCR,
40: .planes = 1,
41: .buffers = 1,
42: .data_offset = { PLANE0_DATA_OFFSET },
43: },
44: {
45: .fourcc = V4L2_PIX_FMT_UYVY,
46: .vdownsampling = { 1 },
47: .bit_depth = { 16 },
48: .color_enc = TGP_COLOR_ENC_YCBCR,
49: .planes = 1,
50: .buffers = 1,
51: },
52: {
53: .fourcc = V4L2_PIX_FMT_YVYU,
54: .vdownsampling = { 1 },
55: .bit_depth = { 16 },
56: .color_enc = TGP_COLOR_ENC_YCBCR,
57: .planes = 1,
58: .buffers = 1,
59: },
60: {
61: .fourcc = V4L2_PIX_FMT_VYUY,
62: .vdownsampling = { 1 },
63: .bit_depth = { 16 },
64: .color_enc = TGP_COLOR_ENC_YCBCR,
65: .planes = 1,
66: .buffers = 1,
67: },
68: {
69: .fourcc = V4L2_PIX_FMT_YUV422P,
70: .vdownsampling = { 1, 1, 1 },
71: .bit_depth = { 8, 4, 4 },
72: .color_enc = TGP_COLOR_ENC_YCBCR,
73: .planes = 3,
74: .buffers = 1,
75: },
76: {
77: .fourcc = V4L2_PIX_FMT_YUV420,
78: .vdownsampling = { 1, 2, 2 },
79: .bit_depth = { 8, 4, 4 },
80: .color_enc = TGP_COLOR_ENC_YCBCR,
81: .planes = 3,
82: .buffers = 1,
83: },
]
|
| 48/2 |
2026/07/17 00:49 |
llm |
expert |
0m
Model:
Tokens:
input: 43325
output: 34
thoughts: 1848
Thoughts: **Analyzing Potential Out-of-Bounds Write in V4L2 Driver**
Okay, let's break this down. My initial thought process is centered around how `sizeimage` is calculated and how that relates to potential buffer overflows. I see that `sizeimage` depends on `bytesperline`, `mp->height`, `vdownsampling`, and `data_offset`. The minimum height constraint is the critical starting point for calculating a minimum buffer size. Since `mp->height` is at least 16 and a related minimum `bytesperline`, this implies a minimum `sizeimage` value.
The real crux of the problem lies in how these parameters are modified and whether those modifications can result in a mismatch between the allocated buffer size and the amount of data actually written. I initially considered if `vivid_vid_cap_s_selection` might be the culprit, but I realized it primarily influences the capture rectangle parameters (`dev->fmt_cap_rect`). While `vivid_vid_cap_s_selection` *does* change the rectangle, the actual buffer allocation is handled by `vb2_core_reqbufs` called in `vivid_s_fmt_vid_cap`.
The important bit to focus on here is the condition using `vb2_is_busy(q)`. If the size of `dev->fmt_cap_rect` changes while buffers are allocated, it will return `-EBUSY`. Now if `dev->has_compose_cap` is true, it changes the `compose` size based on the selection, and maps inside `dev->fmt_cap_rect`. This doesn't seem to have a similar `vb2_is_busy(q)` check, which seems like a potential problem.
However, even though `compose` is modified, it's mapped inside `dev->fmt_cap_rect`, meaning its width can never exceed `mp->width`. Therefore, the data size (`img_width`) will never exceed `bytesperline`. The minimum `bytesperline` is defined by the width of `mp`.
So, since `compose->width` is bounded by `dev->fmt_cap_rect.width`, which in turn is bounded by `mp->width`, and `bytesperline` is based on `mp->width`, the write *shouldn't* exceed buffer bounds... right?
But then I shift focus to `tpg_fill_plane_buffer`, where data is written. It uses `tpg->compose.width` in the calculation for `img_width` and reads `tpg->bytesperline[p]`. `tpg->bytesperline[p]` gets its value from `vivid_s_fmt_vid_cap`. Critically, it appears to be directly set from the user-provided `mp->plane_fmt[p].bytesperline`. *This is the key point!*
We know `tpg->compose.width` is derived from the user-selected rectangle, and that `tpg->bytesperline[p]` is user-set through `mp->plane_fmt[p].bytesperline`. Now, is it possible that `img_width` (derived from `tpg->compose.width`) can be larger than `tpg->bytesperline[p]`?
Let's look more closely at `tpg_hdiv`: `img_width` is calculated as `((x / tpg->hdownsampling[plane]) & tpg->hmask[plane]) * tpg->twopixelsize[plane] / 2`. The critical part is whether `tpg->twopixelsize[plane] / 2` is larger than `fmt->bit_depth[plane] >> 3`. My focus turns to `V4L2_PIX_FMT_NV42`, since it's a common format. If there's a discrepancy between those two calculations, then that leads to the out-of-bounds write!
|
| 49/2 |
2026/07/17 00:49 |
tool |
grepper |
0m
Args: map[Expression:NV42 PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-vid-common.c=34=struct vivid_fmt vivid_formats[] = {
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-132- {
drivers/media/test-drivers/vivid/vivid-vid-common.c:133: .fourcc = V4L2_PIX_FMT_NV42,
drivers/media/test-drivers/vivid/vivid-vid-common.c-134- .vdownsampling = { 1, 1 },
]
|
| 50/2 |
2026/07/17 00:49 |
llm |
expert |
0m
Model:
Tokens:
input: 46222
output: 47
thoughts: 17
Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience and written in the first person:
**Navigating the Codebase**
Okay, let's zero in on `vivid_formats`. I recall seeing that variable referenced around line 132 – likely in a formatting or parsing context. Given my experience, I'm immediately curious about *how* it's being used there. Is it a list, a dictionary, an object with specific attributes? Understanding the data structure is crucial for predicting potential issues with different input formats or understanding the logic behind the handling of certain display or data output concerns. I expect to find some critical format validation or conversion logic in that vicinity. Let's see what’s going on...
|
| 51/2 |
2026/07/17 00:49 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-common.c FirstLine:125 LineCount:20]
Results: map[Contents: 125: .fourcc = V4L2_PIX_FMT_NV24,
126: .vdownsampling = { 1, 1 },
127: .bit_depth = { 8, 16 },
128: .color_enc = TGP_COLOR_ENC_YCBCR,
129: .planes = 2,
130: .buffers = 1,
131: },
132: {
133: .fourcc = V4L2_PIX_FMT_NV42,
134: .vdownsampling = { 1, 1 },
135: .bit_depth = { 8, 16 },
136: .color_enc = TGP_COLOR_ENC_YCBCR,
137: .planes = 2,
138: .buffers = 1,
139: },
140: {
141: .fourcc = V4L2_PIX_FMT_YUV555, /* uuuvvvvv ayyyyyuu */
142: .vdownsampling = { 1 },
143: .bit_depth = { 16 },
144: .planes = 1,
]
|
| 52/2 |
2026/07/17 00:49 |
llm |
expert |
0m
Model:
Tokens:
input: 46804
output: 38
thoughts: 203
Thoughts: **Analyzing Pixel Format NV42 and Potential Discrepancies**
Okay, let's break down this `NV42` pixel format and ensure consistency. My immediate concern is the `bit_depth` for plane 1. We're looking at a bit depth of 16, which translates to `16 >> 3 = 2` bytes per pixel. Makes sense, that's straightforward.
Now, let's cross-reference this with the `tpg_s_fourcc` implementation. Specifically, the NV42 case:
```c
case V4L2_PIX_FMT_NV42:
tpg->twopixelsize[0] = 2;
tpg->twopixelsize[1] = 4;
break;
```
We see `twopixelsize[1]` is set to 4. And indeed, `twopixelsize[1] / 2 = 2` bytes per pixel. So far, so good. The calculation aligns perfectly with the bit depth-derived value. This is expected, but worth verifying.
Now, the natural next step is to expand this check to other formats. I need to scan `tpg_s_fourcc` for any possible mismatches with the defined `vivid_formats`. The NV42 case seems clean, but a comprehensive review is essential. We need to be confident that this consistency holds across the board to avoid future issues. A quick check of the relevant functions is next.
|
| 53/2 |
2026/07/17 00:50 |
tool |
grepper |
0m
Args: map[Expression:twopixelsize PathPrefix:drivers/media/common/v4l2-tpg/]
Results: map[Output:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=211=bool tpg_s_fourcc(struct tpg_data *tpg, u32 fourcc)
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-388- case V4L2_PIX_FMT_RGB332:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:389: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-390- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-425- case V4L2_PIX_FMT_Z16:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:426: tpg->twopixelsize[0] = 2 * 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-427- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-430- case V4L2_PIX_FMT_HSV24:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:431: tpg->twopixelsize[0] = 2 * 3;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-432- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-451- case V4L2_PIX_FMT_HSV32:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:452: tpg->twopixelsize[0] = 2 * 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-453- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-465- case V4L2_PIX_FMT_SRGGB8:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:466: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:467: tpg->twopixelsize[1] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-468- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-480- case V4L2_PIX_FMT_SBGGR16:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:481: tpg->twopixelsize[0] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:482: tpg->twopixelsize[1] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-483- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-492- case V4L2_PIX_FMT_YVU420M:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:493: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:494: tpg->twopixelsize[1] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:495: tpg->twopixelsize[2] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-496- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-498- case V4L2_PIX_FMT_NV42:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:499: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:500: tpg->twopixelsize[1] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-501- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=523=void tpg_reset_source(struct tpg_data *tpg, unsigned width, unsigned height,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-541- for (p = 0; p < tpg->planes; p++)
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:542: tpg->bytesperline[p] = (width * tpg->twopixelsize[p]) /
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-543- (2 * tpg->hdownsampling[p]);
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1133=static void gen_twopix(struct tpg_data *tpg,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1135-{
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1136: unsigned offset = odd * tpg->twopixelsize[0] / 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1137- u8 alpha = tpg->alpha_component;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1790=static void tpg_precalculate_line(struct tpg_data *tpg)
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1847- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1848: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1849- unsigned hdiv = tpg->hdownsampling[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1877- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1878: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1879- u8 *pos = tpg->contrast_line[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1887- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1888: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1889- u8 *pos = tpg->black_line[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1898- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1899: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1900- u8 *pos = tpg->random_line[p] + x * twopixsize / 2;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1997=void tpg_gen_text(const struct tpg_data *tpg, u8 *basep[TPG_MAX_PLANES][2],
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2029- /* Print text */
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2030: switch (tpg->twopixelsize[p]) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2031- case 2:
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=2629=void tpg_fill_plane_buffer(struct tpg_data *tpg, v4l2_std_id std,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2645- params.is_60hz = std & V4L2_STD_525_60;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2646: params.twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2647- params.img_width = tpg_hdiv(tpg, p, tpg->compose.width);
]
|
| 54/2 |
2026/07/17 00:50 |
llm |
expert |
0m
Model:
Tokens:
input: 50187
output: 34
thoughts: 77
Thoughts: Okay, let me process this quickly.
**Analyzing Color Format Pixel Size Assignments**
Right, I'm seeing something interesting here. For the `HSV24` format, the code is setting `tpg->twopixelsize[0]` to `2 * 3`. But then, for `HSV32`, it's `2 * 4`. My immediate thought is, "Okay, why the difference?". It's an important detail to understand the memory allocation. The obvious next step is to correlate this with the characteristics of these formats. I should investigate `vivid_formats` to understand the pixel structure. I'll need to check the bit depths of the individual color channels within `HSV24` and `HSV32` to see if the allocation makes sense, or if there's an error.
|
| 55/2 |
2026/07/17 00:50 |
tool |
grepper |
0m
Args: map[Expression:HSV24 PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-vid-common.c=34=struct vivid_fmt vivid_formats[] = {
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-651- {
drivers/media/test-drivers/vivid/vivid-vid-common.c:652: .fourcc = V4L2_PIX_FMT_HSV24, /* HSV 24bits */
drivers/media/test-drivers/vivid/vivid-vid-common.c-653- .color_enc = TGP_COLOR_ENC_HSV,
]
|
| 56/2 |
2026/07/17 00:50 |
llm |
expert |
0m
Model:
Tokens:
input: 50640
output: 47
thoughts: 17
Thoughts: Here's my attempt at summarizing the thought process, tailored for an expert audience:
**Analyzing `vivid_formats` at Line 651**
Okay, let's zero in on `vivid_formats` around line 651 of the code. My immediate thought is, "What's the context?" I need to understand how `vivid_formats` is being used, declared, and what other variables or functions are interacting with it in that immediate scope. Given that line number, it's probably within a fairly complex function. I need to quickly identify if it's a data structure (likely), a function (less likely, but possible), or a literal. Based on the variable name, "vivid," I'm expecting something related to image or graphical data formats. Could be a lookup table, a configuration object, or even a set of regular expressions for parsing.
I'm mentally preparing to look for its type definition if it's declared in this code base. Is it a custom class? An enum? A simple list or dictionary? I'm anticipating some form of type hinting, given that we are at line 651.
Once I've established its type, I'll be looking for where its members are called, or the object is used, the logic will fall into place. That tells me if it's the right format for me. The goal is to see how this impacts performance or other system characteristics. Is this where they define accepted image formats, color depths, compression types, or something else of that nature? Knowing the function context will make this clear. I'm expecting some kind of parsing or conversion logic. Given this level of focus, I need to understand this to determine if the choices are well-engineered from a usability and performance perspective.
|
| 57/2 |
2026/07/17 00:50 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-common.c FirstLine:645 LineCount:20]
Results: map[Contents: 645: .fourcc = V4L2_PIX_FMT_SRGGB16, /* Bayer RG/GB */
646: .vdownsampling = { 1 },
647: .bit_depth = { 16 },
648: .planes = 1,
649: .buffers = 1,
650: },
651: {
652: .fourcc = V4L2_PIX_FMT_HSV24, /* HSV 24bits */
653: .color_enc = TGP_COLOR_ENC_HSV,
654: .vdownsampling = { 1 },
655: .bit_depth = { 24 },
656: .planes = 1,
657: .buffers = 1,
658: },
659: {
660: .fourcc = V4L2_PIX_FMT_HSV32, /* HSV 32bits */
661: .color_enc = TGP_COLOR_ENC_HSV,
662: .vdownsampling = { 1 },
663: .bit_depth = { 32 },
664: .planes = 1,
]
|
| 58/2 |
2026/07/17 00:50 |
llm |
expert |
0m
Model:
Tokens:
input: 51439
output: 35
thoughts: 1041
Thoughts: **Analyzing Buffer Allocation and Potential Out-of-Bounds Writes**
Okay, so I'm looking at how this `bit_depth` and `bytesperpixel` stuff works for `HSV24`. It's pretty straightforward, `24` bit depth means `3` bytes per pixel. The `twopixelsize` calculation seems consistent too. The potential issue I see arises when we consider the interaction between `tpg->bytesperline` and how the buffer sizes are set up.
I'm zeroing in on this `tpg_s_bytesperline` function. It seems that `vivid_s_fmt_vid_cap` sets it, iterating through a number of buffers which are passed to the function. Now I see that `tpg_s_bytesperline` has some special logic if `tpg->buffers == 1`. In that case, the `bytesperline` values for all the planes are calculated based on the `bpl` value of plane 0. I need to keep this in mind when I think about it for this current structure.
Interestingly, this whole `bytesperline` concept appears to just be the stride. But that still leaves me wondering about how the image width is calculated because that will determine the buffer size. I remember that the image width is `tpg_hdiv(tpg, p, tpg->compose.width)`. It looks like this calculation is independent of `bytesperline`. So that suggests that if the calculated `img_width` is too big, it could lead to an out-of-bounds write, regardless of the stride.
The buffer size is `pfmt[p].sizeimage`. For plane 0, the `sizeimage` is based on `bytesperline`, the height, and the vertical downsampling factor, plus an offset. Crucially, if `tpg->buffers == 1`, the `sizeimage` for plane 0 seems to include *all* the planes' sizes. So it seems like `sizeimage` *should* be big enough to handle all the planes together.
Now, if `sizeimage` *is* big enough, why are we getting out-of-bounds writes? Perhaps it's because `tpg_fill_plane_buffer` is called individually for *each* plane. Let me check the code for `plane_vaddr` to see what is happening.
|
| 59/2 |
2026/07/17 00:51 |
tool |
grepper |
0m
Args: map[Expression:plane_vaddr PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-kthread-cap.c=145=static void vivid_precalc_copy_rects(struct vivid_dev *dev, struct vivid_dev *out_dev)
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-201-
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:202:static void *plane_vaddr(struct tpg_data *tpg, struct vivid_buffer *buf,
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-203- unsigned p, unsigned bpl[TPG_MAX_PLANES], unsigned h)
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-208- if (p == 0 || tpg_g_buffers(tpg) > 1)
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:209: return vb2_plane_vaddr(&buf->vb.vb2_buf, p);
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:210: vbuf = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-211- for (i = 0; i < p; i++)
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c=216=static noinline_for_stack int vivid_copy_buffer(struct vivid_dev *dev,
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-258-
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:259: voutbuf = plane_vaddr(tpg, vid_out_buf, p,
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-260- out_dev->bytesperline_out, out_dev->fmt_out_rect.height);
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c=387=static void vivid_fillbuff(struct vivid_dev *dev, struct vivid_buffer *buf)
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-454- for (p = 0; p < tpg_g_planes(tpg); p++) {
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:455: void *vbuf = plane_vaddr(tpg, buf, p,
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-456- tpg->bytesperline, tpg->buf_height);
--
drivers/media/test-drivers/vivid/vivid-meta-cap.c=157=void vivid_meta_cap_fillbuff(struct vivid_dev *dev,
--
drivers/media/test-drivers/vivid/vivid-meta-cap.c-159-{
drivers/media/test-drivers/vivid/vivid-meta-cap.c:160: struct vivid_uvc_meta_buf *meta = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
drivers/media/test-drivers/vivid/vivid-meta-cap.c-161- int buf_off = 0;
--
drivers/media/test-drivers/vivid/vivid-meta-out.c=157=void vivid_meta_out_process(struct vivid_dev *dev,
--
drivers/media/test-drivers/vivid/vivid-meta-out.c-159-{
drivers/media/test-drivers/vivid/vivid-meta-out.c:160: struct vivid_meta_out_buf *meta = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
drivers/media/test-drivers/vivid/vivid-meta-out.c-161-
--
drivers/media/test-drivers/vivid/vivid-sdr-cap.c=518=void vivid_sdr_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
drivers/media/test-drivers/vivid/vivid-sdr-cap.c-519-{
drivers/media/test-drivers/vivid/vivid-sdr-cap.c:520: u8 *vbuf = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
drivers/media/test-drivers/vivid/vivid-sdr-cap.c-521- unsigned long i;
--
drivers/media/test-drivers/vivid/vivid-touch-cap.c=251=void vivid_fillbuff_tch(struct vivid_dev *dev, struct vivid_buffer *buf)
--
drivers/media/test-drivers/vivid/vivid-touch-cap.c-257-
drivers/media/test-drivers/vivid/vivid-touch-cap.c:258: __s16 *tch_buf = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
drivers/media/test-drivers/vivid/vivid-touch-cap.c-259-
--
drivers/media/test-drivers/vivid/vivid-vbi-cap.c=83=void vivid_raw_vbi_cap_process(struct vivid_dev *dev, struct vivid_buffer *buf)
--
drivers/media/test-drivers/vivid/vivid-vbi-cap.c-85- struct v4l2_vbi_format vbi;
drivers/media/test-drivers/vivid/vivid-vbi-cap.c:86: u8 *vbuf = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
drivers/media/test-drivers/vivid/vivid-vbi-cap.c-87-
--
drivers/media/test-drivers/vivid/vivid-vbi-cap.c=102=void vivid_sliced_vbi_cap_process(struct vivid_dev *dev,
--
drivers/media/test-drivers/vivid/vivid-vbi-cap.c-105- struct v4l2_sliced_vbi_data *vbuf =
drivers/media/test-drivers/vivid/vivid-vbi-cap.c:106: vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
drivers/media/test-drivers/vivid/vivid-vbi-cap.c-107-
--
drivers/media/test-drivers/vivid/vivid-vbi-out.c=216=void vivid_sliced_vbi_out_process(struct vivid_dev *dev,
--
drivers/media/test-drivers/vivid/vivid-vbi-out.c-219- struct v4l2_sliced_vbi_data *vbi =
drivers/media/test-drivers/vivid/vivid-vbi-out.c:220: vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
drivers/media/test-drivers/vivid/vivid-vbi-out.c-221- unsigned elems =
]
|
| 60/2 |
2026/07/17 00:51 |
llm |
expert |
0m
Model:
Tokens:
input: 54898
output: 48
thoughts: 22
Thoughts: Okay, let's dive into this. Here's my take on those thoughts, as if they're my own:
**Analyzing `plane_vaddr` in `vivid-kthread-cap.c`**
Alright, the next step is to get into the details of this `plane_vaddr` variable within the `vivid-kthread-cap.c` file. I need to refresh my memory on how this component is architected. I'm assuming, given the naming, that this relates to the virtual address space and capabilities within the kernel thread context of this "vivid" component. I'm going to want to understand: is this a per-thread mapping? How is it managed and allocated? Are there any obvious potential vulnerabilities or concurrency issues in how it's used? Any potential for address space layout issues? Right now, I'm thinking about the potential attack surfaces here – specifically, where can an attacker manipulate this data or influence its use to gain privileges, leak information, or cause a denial of service. The code review begins!
|
| 61/2 |
2026/07/17 00:51 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-kthread-cap.c FirstLine:200 LineCount:20]
Results: map[Contents: 200: }
201:
202: static void *plane_vaddr(struct tpg_data *tpg, struct vivid_buffer *buf,
203: unsigned p, unsigned bpl[TPG_MAX_PLANES], unsigned h)
204: {
205: unsigned i;
206: void *vbuf;
207:
208: if (p == 0 || tpg_g_buffers(tpg) > 1)
209: return vb2_plane_vaddr(&buf->vb.vb2_buf, p);
210: vbuf = vb2_plane_vaddr(&buf->vb.vb2_buf, 0);
211: for (i = 0; i < p; i++)
212: vbuf += bpl[i] * h / tpg->vdownsampling[i];
213: return vbuf;
214: }
215:
216: static noinline_for_stack int vivid_copy_buffer(struct vivid_dev *dev,
217: struct vivid_dev *out_dev, unsigned p,
218: u8 *vcapbuf, struct vivid_buffer *vid_cap_buf)
219: {
]
|
| 62/2 |
2026/07/17 00:51 |
llm |
expert |
0m
Model:
Tokens:
input: 55552
output: 38
thoughts: 2192
Thoughts: **Analyzing the TPG and Buffer Calculations**
Okay, let's break this down. First, the `plane_vaddr` calculation seems straightforward enough. It leverages `bytesperline` and `buf_height`, which makes sense. I see that `buf_height` is derived from `dev->fmt_cap_rect.height`, which is directly tied to the capture format's height (`mp->height`). The `bytesperline` is also correctly derived and adjusted using `vdownsampling`. This aligns perfectly with how `sizeimage` is computed. So, as far as I can tell, the base address calculation for each plane is *correct*. The formula, in essence, adds the offset of each plane to an initially provided buffer address.
Now, the issue is that `tpg_fill_plane_buffer` is doing an out-of-bounds write. Let's trace it. It calculates `buf_line` using `tpg_calc_buffer_line`. Okay, that adds `tpg->compose.top` to the vertical coordinate. It looks like `buf_line` is then used as an index into the buffer, multiplied by `params.stride` (which is `tpg->bytesperline[p]`). I carefully examined the possible scenarios: `buf_line` can range up to `tpg->compose.top + tpg->compose.height - 1`, and the constraints ensure that the calculation does not exceed plane boundary. It is clear that `buf_line * params.stride` should be within the plane, and the width of the write (`img_width`) should also be within a reasonable limit.
Given the code, the offsets from `vbuf` seem valid. The write occurs in the loop, where the buffer line offset, and then the width of the buffer line is calculated.
The reported bug says that there is a write of 5120 bytes in a 4096-byte (1-page) vmalloc region. This suggests that the issue might stem from an inconsistency in the size of the buffer that is allocated, or the requested size vs. the actual size of the write. Somehow, we have a calculation error that leads to an overflow.
But how can the write width (5120) exceed the buffer size if all the calculations are right, based on the sizes? The calculation of the `sizeimage` (and hence the buffer size) depends on the format parameters, but the buffer seems to be only 4096 bytes large.
My immediate suspicion is that there is an issue during the buffer allocation in `vb2_core_reqbufs`. Somehow, the buffer size requested is not what's being provided and returned. It is possible that the buffer's alignment constraints cause problems, or that some other part of the system is not calculating things correctly.
I need to check how the plane sizes are determined through `vid_cap_queue_setup` to understand how the allocation happens.
|
| 63/2 |
2026/07/17 00:51 |
tool |
grepper |
0m
Args: map[Expression:vid_cap_queue_setup PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-vid-cap.c=62=static inline unsigned int webcam_ival_count(const struct vivid_dev *dev,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-77-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:78:static int vid_cap_queue_setup(struct vb2_queue *vq,
drivers/media/test-drivers/vivid/vivid-vid-cap.c-79- unsigned *nbuffers, unsigned *nplanes,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=255=const struct vb2_ops vivid_vid_cap_qops = {
drivers/media/test-drivers/vivid/vivid-vid-cap.c:256: .queue_setup = vid_cap_queue_setup,
drivers/media/test-drivers/vivid/vivid-vid-cap.c-257- .buf_prepare = vid_cap_buf_prepare,
]
|
| 64/2 |
2026/07/17 00:51 |
llm |
expert |
0m
Model:
Tokens:
input: 58694
output: 46
thoughts: 13
Thoughts: Okay, let's dive into this. Here's my take on those thoughts, as though they were my own:
**Analyzing `vid_cap_queue_setup`**
Alright, time to get into `vid_cap_queue_setup`. I see the name, which immediately suggests initialization or configuration related to a video capture queue. My expertise tells me this likely revolves around handling video frames, maybe buffering, and coordinating data flow from a video input source. I'm already mentally running through the typical elements: allocation of memory, setup of data structures to manage the queue, potential thread synchronization primitives (mutexes, semaphores), and maybe some checks for resource availability. I'm expecting to see specific calls to the underlying video capture API, perhaps something like V4L2 or DirectShow, depending on the system this code is written for. I anticipate there'll be error handling, which is crucial in this type of real-time application. I'll be looking to understand the trade-offs implemented; are they prioritizing low latency, high throughput, or some balance? Are they implementing any frame dropping mechanisms? Essentially, this function is the backbone of the capture process. I'm keen to grasp the nuances here.
|
| 65/2 |
2026/07/17 00:52 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-cap.c FirstLine:78 LineCount:50]
Results: map[Contents: 78: static int vid_cap_queue_setup(struct vb2_queue *vq,
79: unsigned *nbuffers, unsigned *nplanes,
80: unsigned sizes[], struct device *alloc_devs[])
81: {
82: struct vivid_dev *dev = vb2_get_drv_priv(vq);
83: unsigned buffers = tpg_g_buffers(&dev->tpg);
84: unsigned h = dev->fmt_cap_rect.height;
85: unsigned p;
86:
87: if (dev->field_cap == V4L2_FIELD_ALTERNATE) {
88: /*
89: * You cannot use read() with FIELD_ALTERNATE since the field
90: * information (TOP/BOTTOM) cannot be passed back to the user.
91: */
92: if (vb2_fileio_is_active(vq))
93: return -EINVAL;
94: }
95:
96: if (dev->queue_setup_error) {
97: /*
98: * Error injection: test what happens if queue_setup() returns
99: * an error.
100: */
101: dev->queue_setup_error = false;
102: return -EINVAL;
103: }
104: if (*nplanes) {
105: /*
106: * Check if the number of requested planes match
107: * the number of buffers in the current format. You can't mix that.
108: */
109: if (*nplanes != buffers)
110: return -EINVAL;
111: for (p = 0; p < buffers; p++) {
112: if (sizes[p] < tpg_g_line_width(&dev->tpg, p) * h /
113: dev->fmt_cap->vdownsampling[p] +
114: dev->fmt_cap->data_offset[p])
115: return -EINVAL;
116: }
117: } else {
118: for (p = 0; p < buffers; p++)
119: sizes[p] = (tpg_g_line_width(&dev->tpg, p) * h) /
120: dev->fmt_cap->vdownsampling[p] +
121: dev->fmt_cap->data_offset[p];
122: }
123:
124: *nplanes = buffers;
125:
126: dprintk(dev, 1, "%s: count=%d\n", __func__, *nbuffers);
127: for (p = 0; p < buffers; p++)
]
|
| 66/2 |
2026/07/17 00:52 |
llm |
expert |
0m
Model:
Tokens:
input: 59786
output: 35
thoughts: 699
Thoughts: **Analyzing Buffer Size Calculation in `vid_cap_queue_setup`**
Okay, let's break this down. It looks like `vid_cap_queue_setup` is responsible for calculating buffer sizes, specifically through this line:
```c
for (p = 0; p < buffers; p++)
sizes[p] = (tpg_g_line_width(&dev->tpg, p) * h) /
dev->fmt_cap->vdownsampling[p] +
dev->fmt_cap->data_offset[p];
```
I see that `tpg_g_line_width` actually returns `tpg->bytesperline[p]`. Got it. Now, the interesting part is what happens when `*nplanes` isn't zero, which is the case when `VIDIOC_CREATE_BUFS` is called. It then validates:
```c
for (p = 0; p < buffers; p++) {
if (sizes[p] < tpg_g_line_width(&dev->tpg, p) * h /
dev->fmt_cap->vdownsampling[p] +
dev->fmt_cap->data_offset[p])
return -EINVAL;
}
```
Aha, that means if we use `VIDIOC_CREATE_BUFS`, the user *provides* `sizes[p]`. But `vid_cap_queue_setup` *checks* if the user-provided size is large enough: at least `tpg_g_line_width * h / vdownsampling + data_offset`. If `h` is 0, the first component becomes 0. That looks suspicious.
So, if `h` is 0, the code would accept a size of 0 (or `data_offset`, which may also be 0). Then `vb2_core_reqbufs` or `vb2_core_create_bufs` will allocate a buffer of size `sizes[p]`. Wait, what does `h` represent? Oh, it's `dev->fmt_cap_rect.height`.
Can `dev->fmt_cap_rect.height` be 0? Let's see... in `vivid_try_fmt_vid_cap`, it looks like `v4l2_rect_set_min_size` is called with `vivid_min_rect`. And `vivid_min_rect` has `height = 16`. So `dev->fmt_cap_rect.height` is *at least* 16.
This means `tpg_g_line_width * h / vdownsampling` is at least `tpg_g_line_width * 16`. And consequently, `sizes[p]` *must* be at least `tpg_g_line_width * 16`. Now, if `tpg_g_line_width` is 5120, `sizes[p]` would need to be at least `5120 * 16 = 81920` bytes.
But the bug report states that the buffer is only 4096 bytes! Something isn't adding up. How is it even possible to get a buffer of size 4096 when it should be at least 81920? I need to double-check that `tpg_g_line_width` value.
|
| 67/2 |
2026/07/17 00:52 |
tool |
grepper |
0m
Args: map[Expression:tpg_g_line_width PathPrefix:include/media/tpg/]
Results: map[Output:include/media/tpg/v4l2-tpg.h=462=static inline void tpg_s_bytesperline(struct tpg_data *tpg, unsigned plane, unsigned bpl)
--
include/media/tpg/v4l2-tpg.h-480-
include/media/tpg/v4l2-tpg.h:481:static inline unsigned tpg_g_line_width(const struct tpg_data *tpg, unsigned plane)
include/media/tpg/v4l2-tpg.h-482-{
]
|
| 68/2 |
2026/07/17 00:52 |
llm |
expert |
0m
Model:
Tokens:
input: 61434
output: 44
thoughts: 33
Thoughts: Okay, let's dive into this. Here's my thought process on the matter:
**Analyzing `tpg_g_line_width`**
Right, so I need to get a clear understanding of `tpg_g_line_width`. The first logical step is to pinpoint its declaration. That means going straight into `include/media/tpg/v4l2-tpg.h`. I'm assuming, given the naming convention and location, this is related to some kind of test pattern generator within the V4L2 framework. Let's see what the header file reveals. I'm expecting to find the relevant structure definition and probably some related macros or enums. Hopefully, the comments are clear enough to quickly grasp its purpose and usage within the overall architecture. I'm particularly interested in how it's handled in relation to other parameters, and how it aligns with the overall TPG (Test Pattern Generator) functionality. Time to dig in and understand this parameter's role.
|
| 69/2 |
2026/07/17 00:52 |
tool |
read-file |
0m
Args: map[File:include/media/tpg/v4l2-tpg.h FirstLine:475 LineCount:20]
Results: map[Contents: 475: }
476: if (tpg_g_interleaved(tpg))
477: tpg->bytesperline[1] = tpg->bytesperline[0];
478: }
479:
480:
481: static inline unsigned tpg_g_line_width(const struct tpg_data *tpg, unsigned plane)
482: {
483: unsigned w = 0;
484: unsigned p;
485:
486: if (tpg->buffers > 1)
487: return tpg_g_bytesperline(tpg, plane);
488: for (p = 0; p < tpg_g_planes(tpg); p++) {
489: unsigned plane_w = tpg_g_bytesperline(tpg, p);
490:
491: w += plane_w / tpg->vdownsampling[p];
492: }
493: return w;
494: }
]
|
| 70/2 |
2026/07/17 00:52 |
llm |
expert |
0m
Model:
Tokens:
input: 62031
output: 38
thoughts: 1936
Thoughts: **Analyzing the Buffer Size Discrepancy**
Okay, let's break this down systematically. My initial thought was that `tpg_g_line_width` was computing something, but it's really returning `w`, which is based on a calculation involving `bytesperline` and `vdownsampling`. The `vid_cap_queue_setup` function then uses this `w` and height `h` to calculate buffer sizes. I was initially concerned about a double application of `vdownsampling`, but I see that's part of the intended calculation.
If we look at `sizes[0]` and do the math, it seems like the result should be `(sum(bytesperline[i] / vdownsampling[i])) * h / vdownsampling[0]`. Now, if we consider `vivid_try_fmt_vid_cap`, its calculations seem mathematically sound but it uses a different calculation.
The puzzle arises when considering the reported 4096-byte buffer size, given an `img_width` of 5120 and the expected calculation. We know that if we can get a `w` large enough for the images, then the buffer size should be quite large, far greater than 4096 bytes.
My first thought was that somehow `tpg->compose.width` might be changed *after* the buffer allocation and it was bigger, but `v4l2_rect_map_inside` restricts the `compose->width` to be smaller than or equal to `dev->fmt_cap_rect.width`. So that is not the issue, and, further, the `vivid_vid_cap_s_selection` and `vivid_s_fmt_vid_cap` functions *should* return `-EBUSY` if the buffer size or format changes while buffers are allocated.
So, how can this happen? We know that `img_width` is calculated using `tpg_hdiv`, meaning it's dependent on `tpg->compose.width`, but that the buffers are not affected by this. That makes me wonder, could there be an issue with `tpg_hdiv` itself? Specifically, what if `twopixelsize / 2` is much larger than `bit_depth >> 3`? The calculation for `img_width` depends on this, and the calculations for the buffer size are independent. That could explain this.
I'll need to go back and check the formats to see if any have a disparity in `twopixelsize / 2` and `bit_depth >> 3` that's big enough to cause this discrepancy. If I can identify such a format, that would indicate where the issue lies.
|
| 71/2 |
2026/07/17 00:52 |
tool |
grepper |
0m
Args: map[Expression:twopixelsize PathPrefix:drivers/media/common/v4l2-tpg/]
Results: map[Output:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=211=bool tpg_s_fourcc(struct tpg_data *tpg, u32 fourcc)
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-388- case V4L2_PIX_FMT_RGB332:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:389: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-390- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-425- case V4L2_PIX_FMT_Z16:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:426: tpg->twopixelsize[0] = 2 * 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-427- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-430- case V4L2_PIX_FMT_HSV24:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:431: tpg->twopixelsize[0] = 2 * 3;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-432- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-451- case V4L2_PIX_FMT_HSV32:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:452: tpg->twopixelsize[0] = 2 * 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-453- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-465- case V4L2_PIX_FMT_SRGGB8:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:466: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:467: tpg->twopixelsize[1] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-468- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-480- case V4L2_PIX_FMT_SBGGR16:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:481: tpg->twopixelsize[0] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:482: tpg->twopixelsize[1] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-483- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-492- case V4L2_PIX_FMT_YVU420M:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:493: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:494: tpg->twopixelsize[1] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:495: tpg->twopixelsize[2] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-496- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-498- case V4L2_PIX_FMT_NV42:
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:499: tpg->twopixelsize[0] = 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:500: tpg->twopixelsize[1] = 4;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-501- break;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=523=void tpg_reset_source(struct tpg_data *tpg, unsigned width, unsigned height,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-541- for (p = 0; p < tpg->planes; p++)
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:542: tpg->bytesperline[p] = (width * tpg->twopixelsize[p]) /
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-543- (2 * tpg->hdownsampling[p]);
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1133=static void gen_twopix(struct tpg_data *tpg,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1135-{
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1136: unsigned offset = odd * tpg->twopixelsize[0] / 2;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1137- u8 alpha = tpg->alpha_component;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1790=static void tpg_precalculate_line(struct tpg_data *tpg)
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1847- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1848: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1849- unsigned hdiv = tpg->hdownsampling[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1877- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1878: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1879- u8 *pos = tpg->contrast_line[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1887- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1888: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1889- u8 *pos = tpg->black_line[p];
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1898- for (p = 0; p < tpg->planes; p++) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:1899: unsigned twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-1900- u8 *pos = tpg->random_line[p] + x * twopixsize / 2;
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=1997=void tpg_gen_text(const struct tpg_data *tpg, u8 *basep[TPG_MAX_PLANES][2],
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2029- /* Print text */
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2030: switch (tpg->twopixelsize[p]) {
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2031- case 2:
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c=2629=void tpg_fill_plane_buffer(struct tpg_data *tpg, v4l2_std_id std,
--
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2645- params.is_60hz = std & V4L2_STD_525_60;
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2646: params.twopixsize = tpg->twopixelsize[p];
drivers/media/common/v4l2-tpg/v4l2-tpg-core.c-2647- params.img_width = tpg_hdiv(tpg, p, tpg->compose.width);
]
|
| 72/2 |
2026/07/17 00:52 |
llm |
expert |
0m
Model:
Tokens:
input: 67404
output: 53
thoughts: 706
Thoughts: **Analyzing `tpg_s_fourcc` Initialization**
Okay, so I'm looking at this `tpg_s_fourcc` function, and my initial thought is, "Wait, `tpg->twopixelsize[p]` is initialized here." This is key. But then I have to ask myself, is there *any* scenario where `tpg->twopixelsize[p]` *isn't* initialized? That's the core question here. I need to be sure the assumption that it *is* initialized holds true across the board.
I see that the function initializes a bunch of other fields like `fourcc`, `planes`, `buffers`, and some flags. And then there's this `switch` statement based on the `fourcc` value. The important part here seems to be in the "Bayer" cases, where `interleaved` is set to true and there's additional initialization for second plane parameters.
Hold on... I'm noticing this "fall through" from the Bayer formats to the `RGB332` etc. cases. Wait a minute... does this mean that formats like `V4L2_PIX_FMT_SRGGB8` also initialize `tpg->interleaved` and other two-plane variables? That doesn't seem right. It looks like it *does* mean that. It falls through to the single plane RGB formats.
Okay, I need to verify what is supposed to happen in these cases. To be sure, I need to check `tpg_s_fourcc` in `drivers/media/common/v4l2-tpg/v4l2-tpg-core.c` to see if there is another call to it. I need to double-check that the behavior is exactly as I think it is.
|
| 73/2 |
2026/07/17 00:53 |
tool |
read-file |
0m
Args: map[File:drivers/media/common/v4l2-tpg/v4l2-tpg-core.c FirstLine:380 LineCount:50]
Results: map[Contents: 380: tpg->color_enc = TGP_COLOR_ENC_HSV;
381: break;
382: default:
383: return false;
384: }
385:
386: switch (fourcc) {
387: case V4L2_PIX_FMT_GREY:
388: case V4L2_PIX_FMT_RGB332:
389: tpg->twopixelsize[0] = 2;
390: break;
391: case V4L2_PIX_FMT_RGB565:
392: case V4L2_PIX_FMT_RGB565X:
393: case V4L2_PIX_FMT_RGB444:
394: case V4L2_PIX_FMT_XRGB444:
395: case V4L2_PIX_FMT_ARGB444:
396: case V4L2_PIX_FMT_RGBX444:
397: case V4L2_PIX_FMT_RGBA444:
398: case V4L2_PIX_FMT_XBGR444:
399: case V4L2_PIX_FMT_ABGR444:
400: case V4L2_PIX_FMT_BGRX444:
401: case V4L2_PIX_FMT_BGRA444:
402: case V4L2_PIX_FMT_RGB555:
403: case V4L2_PIX_FMT_XRGB555:
404: case V4L2_PIX_FMT_ARGB555:
405: case V4L2_PIX_FMT_RGBX555:
406: case V4L2_PIX_FMT_RGBA555:
407: case V4L2_PIX_FMT_XBGR555:
408: case V4L2_PIX_FMT_ABGR555:
409: case V4L2_PIX_FMT_BGRX555:
410: case V4L2_PIX_FMT_BGRA555:
411: case V4L2_PIX_FMT_RGB555X:
412: case V4L2_PIX_FMT_XRGB555X:
413: case V4L2_PIX_FMT_ARGB555X:
414: case V4L2_PIX_FMT_YUYV:
415: case V4L2_PIX_FMT_UYVY:
416: case V4L2_PIX_FMT_YVYU:
417: case V4L2_PIX_FMT_VYUY:
418: case V4L2_PIX_FMT_YUV444:
419: case V4L2_PIX_FMT_YUV555:
420: case V4L2_PIX_FMT_YUV565:
421: case V4L2_PIX_FMT_Y10:
422: case V4L2_PIX_FMT_Y12:
423: case V4L2_PIX_FMT_Y16:
424: case V4L2_PIX_FMT_Y16_BE:
425: case V4L2_PIX_FMT_Z16:
426: tpg->twopixelsize[0] = 2 * 2;
427: break;
428: case V4L2_PIX_FMT_RGB24:
429: case V4L2_PIX_FMT_BGR24:
]
|
| 74/2 |
2026/07/17 00:53 |
llm |
expert |
0m
Model:
Tokens:
input: 69652
output: 47
thoughts: 1028
Thoughts: **Analyzing a Memory Corruption Bug**
Okay, so `tpg_s_fourcc` initializes `twopixelsize` based on the FourCC code, which makes sense. I was initially wondering if there was some format where `tpg->twopixelsize[0]` could be larger than what's specified in `vivid_formats`, and then I thought about uninitialized elements of the array, but it looks like `twopixelsize` is handled correctly for the formats I've checked.
Specifically looking at `V4L2_PIX_FMT_NV42`, the array is set up as I would expect with `[2, 4]`. The same goes for the `YUV420` formats, which use `[2, 2, 2]`. No issues there.
Now, let's get to the bug report: "Write of size 5120 at addr...". The address belongs to a 1-page vmalloc region allocated by `vb2_vmalloc_alloc`. This indicates the allocation size was exactly one page, meaning `sizeimage` was <= 4096. But the report also says there was a write of size 5120, which is larger than the allocation. How can that happen?
`vb2_vmalloc_alloc` allocates based on `sizeimage`. So the allocation was for 4096 bytes or less. But how can we have a `bytesperline` of 5120 when `sizeimage` is small? The `bytesperline` is based on `mp->width`, and this in turn comes from `tpg_hdiv`, which ultimately depends on `tpg->compose.width` and `twopixelsize`.
If `img_width` is 5120, then the `tpg_hdiv` function is 5120, and `tpg->compose.width * twopixelsize / 2` will be 5120, which gives me a clue: if `twopixelsize / 2` is 4 (like for ARGB32), then `tpg->compose.width` would be 1280. If `tpg->compose.width` is 1280, then `dev->fmt_cap_rect.width` should also be at least 1280, meaning that `mp->width` should be 1280. With `mp->width` being 1280, then `bytesperline` should be at least `1280 * 4 = 5120`. If that is true, then `sizeimage` would be at least `5120 * mp->height`, and if `mp->height` is at least 16 (since this is our minimal height, according to the `vivid_min_rect` variable) then `sizeimage` would be at least `5120 * 16 = 81920`. But `sizeimage` was <= 4096.
This is a problem! The only way to reconcile this is if `mp->height` is somehow zero! However, `vivid_min_rect` sets a minimal height of 16. So... maybe `vivid_try_fmt_vid_cap` doesn't strictly enforce that minimum. I need to re-examine that function.
|
| 75/2 |
2026/07/17 00:54 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-cap.c FirstLine:600 LineCount:20]
Results: map[Contents: 600: }
601: if (V4L2_FIELD_HAS_T_OR_B(mp->field))
602: factor = 2;
603: if (vivid_is_webcam(dev) ||
604: (!dev->has_scaler_cap && !dev->has_crop_cap && !dev->has_compose_cap)) {
605: mp->width = w;
606: mp->height = h / factor;
607: } else {
608: struct v4l2_rect r = { 0, 0, mp->width, mp->height * factor };
609:
610: v4l2_rect_set_min_size(&r, &vivid_min_rect);
611: v4l2_rect_set_max_size(&r, &vivid_max_rect);
612: if (dev->has_scaler_cap && !dev->has_compose_cap) {
613: struct v4l2_rect max_r = { 0, 0, MAX_ZOOM * w, MAX_ZOOM * h };
614:
615: v4l2_rect_set_max_size(&r, &max_r);
616: } else if (!dev->has_scaler_cap && dev->has_crop_cap && !dev->has_compose_cap) {
617: v4l2_rect_set_max_size(&r, &dev->src_rect);
618: } else if (!dev->has_scaler_cap && !dev->has_crop_cap) {
619: v4l2_rect_set_min_size(&r, &dev->src_rect);
]
|
| 76/2 |
2026/07/17 00:54 |
llm |
expert |
0m
Model:
Tokens:
input: 71956
output: 47
thoughts: 1044
Thoughts: **Analyzing the Pixel Buffer Size Calculation**
Okay, so I'm diving into this code that's calculating the pixel buffer size, `sizeimage`, and something isn't adding up. The initial thought is that `mp->height` is calculated directly from `dev->src_rect.height` divided by a `factor`. That's straightforward, assuming a fixed source rectangle. The special cases where scaling or cropping isn't available should be fairly simple.
However, a zero height for `dev->src_rect.height` could be a problem initially, and that I need to keep in mind. Since `dev->src_rect` is initialized within `vivid_create_instance`, I'll need to check if the height can be zero, or it's minimum size. And it turns out it is set based on the `VIDIOC_S_INPUT` call, so it can change, but it is the source rectangle which is not necessarily 0.
If scaling is involved, the calculation becomes more complex. Here, `mp->height` is limited by a minimum size, `vivid_min_rect.height`, which guarantees a minimum height of at least 16 divided by `factor`. If `factor` is 2, then `mp->height` is at least 8. Given this, it looks like a `sizeimage` calculation is `bytesperline * mp->height`, and if `bytesperline` is 5120 and `mp->height` is 8, the result is well above the expected value of 4096.
I'm thinking, does `vdownsampling` affect things? But the maximum value is 2, so the minimum `sizeimage` is at least 20480.
So the `bit_depth` won't be a problem because it's guaranteed to be at least 4. But, wait, is `pfmt[p].bytesperline` always equal to 5120?
In `vivid_try_fmt_vid_cap`, it's not a direct assignment. The value of `bytesperline` is based on `mp->width` and `fmt->bit_depth[p]`. It will always use `mp->width * fmt->bit_depth[p] >> 3`. The code adjusts the requested `bytesperline` (if provided by the user) by setting it to the minimum of `max_bpl` and `bytesperline` which is `mp->width * fmt->bit_depth[p] >> 3` if the requested value is 0.
If the user sets `pfmt[p].bytesperline` to 0, then the calculation results in 64, which is small enough to fit. If `mp->width` is 16 (minimum), `bytesperline` becomes 64, and the resulting `sizeimage` is 512, which is small enough to fit within a page!
But here's where it gets interesting and potentially explains the bug. If `mp->width` is 16, then `dev->fmt_cap_rect.width` is also 16, because of the minimum size defined in the initialization. The `tpg->compose.width` is also less than or equal to 16, since this rectangle is mapped inside `dev->fmt_cap_rect`. Consequently, `img_width = tpg_hdiv(tpg, p, tpg->compose.width)` is at most 64. So how can `img_width` be 5120? Is there a mistake in how `tpg->compose.width` is mapped? Something isn't adding up. I need to re-examine how `vivid_vid_cap_s_selection` handles `tpg->compose.width` to understand this discrepancy better.
|
| 77/2 |
2026/07/17 00:54 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-cap.c FirstLine:990 LineCount:50]
Results: map[Contents: 990: s->r.height *= factor;
991: *crop = s->r;
992: break;
993: case V4L2_SEL_TGT_COMPOSE:
994: if (!dev->has_compose_cap)
995: return -EINVAL;
996: ret = vivid_vid_adjust_sel(s->flags, &s->r);
997: if (ret)
998: return ret;
999: v4l2_rect_set_min_size(&s->r, &vivid_min_rect);
1000: v4l2_rect_set_max_size(&s->r, &dev->fmt_cap_rect);
1001: if (dev->has_scaler_cap) {
1002: struct v4l2_rect max_rect = {
1003: 0, 0,
1004: dev->src_rect.width * MAX_ZOOM,
1005: (dev->src_rect.height / factor) * MAX_ZOOM
1006: };
1007:
1008: v4l2_rect_set_max_size(&s->r, &max_rect);
1009: if (dev->has_crop_cap) {
1010: struct v4l2_rect min_rect = {
1011: 0, 0,
1012: s->r.width / MAX_ZOOM,
1013: (s->r.height * factor) / MAX_ZOOM
1014: };
1015: struct v4l2_rect max_rect = {
1016: 0, 0,
1017: s->r.width * MAX_ZOOM,
1018: (s->r.height * factor) * MAX_ZOOM
1019: };
1020:
1021: v4l2_rect_set_min_size(crop, &min_rect);
1022: v4l2_rect_set_max_size(crop, &max_rect);
1023: v4l2_rect_map_inside(crop, &dev->crop_bounds_cap);
1024: }
1025: } else if (dev->has_crop_cap) {
1026: s->r.top *= factor;
1027: s->r.height *= factor;
1028: v4l2_rect_set_max_size(&s->r, &dev->src_rect);
1029: v4l2_rect_set_size_to(crop, &s->r);
1030: v4l2_rect_map_inside(crop, &dev->crop_bounds_cap);
1031: s->r.top /= factor;
1032: s->r.height /= factor;
1033: } else {
1034: v4l2_rect_set_size_to(&s->r, &dev->src_rect);
1035: s->r.height /= factor;
1036: }
1037: v4l2_rect_map_inside(&s->r, &dev->fmt_cap_rect);
1038: *compose = s->r;
1039: break;
]
|
| 78/2 |
2026/07/17 00:54 |
llm |
expert |
0m
Model:
Tokens:
input: 74792
output: 47
thoughts: 162
Thoughts: **Analyzing Video4Linux2 Selection Targets**
Okay, let's break this down. In `V4L2_SEL_TGT_COMPOSE`, I see this snippet of code:
```c
v4l2_rect_map_inside(&s->r, &dev->fmt_cap_rect);
*compose = s->r;
```
Right, it's mapping `s->r` (which I assume is a rectangle) to be *inside* `dev->fmt_cap_rect`. The critical takeaway is that this implicitly guarantees `compose->width` is less than or equal to `dev->fmt_cap_rect.width`, and the same for height. This is a crucial constraint. This will *always* be the case.
But wait... what happens if `dev->fmt_cap_rect` is modified *before* `V4L2_SEL_TGT_COMPOSE` is called? I need to consider all the possibilities here. I'm thinking specifically about `V4L2_SEL_TGT_CROP`. I need to review how `vivid_vid_cap_s_selection` handles `V4L2_SEL_TGT_CROP` because *that* might be the source of some potentially tricky interactions. I need to make sure the constraint holds *regardless* of earlier cropping operations. Time to check that function...
|
| 79/2 |
2026/07/17 00:54 |
tool |
read-file |
0m
Args: map[File:drivers/media/test-drivers/vivid/vivid-vid-cap.c FirstLine:930 LineCount:50]
Results: map[Contents: 930:
931: switch (s->target) {
932: case V4L2_SEL_TGT_CROP:
933: if (!dev->has_crop_cap)
934: return -EINVAL;
935: ret = vivid_vid_adjust_sel(s->flags, &s->r);
936: if (ret)
937: return ret;
938: v4l2_rect_set_min_size(&s->r, &vivid_min_rect);
939: v4l2_rect_set_max_size(&s->r, &dev->src_rect);
940: v4l2_rect_map_inside(&s->r, &dev->crop_bounds_cap);
941: s->r.top /= factor;
942: s->r.height /= factor;
943: if (dev->has_scaler_cap) {
944: struct v4l2_rect fmt = dev->fmt_cap_rect;
945: struct v4l2_rect max_rect = {
946: 0, 0,
947: s->r.width * MAX_ZOOM,
948: s->r.height * MAX_ZOOM
949: };
950: struct v4l2_rect min_rect = {
951: 0, 0,
952: s->r.width / MAX_ZOOM,
953: s->r.height / MAX_ZOOM
954: };
955:
956: v4l2_rect_set_min_size(&fmt, &min_rect);
957: if (!dev->has_compose_cap)
958: v4l2_rect_set_max_size(&fmt, &max_rect);
959: if (!v4l2_rect_same_size(&dev->fmt_cap_rect, &fmt) &&
960: vb2_is_busy(&dev->vb_vid_cap_q))
961: return -EBUSY;
962: if (dev->has_compose_cap) {
963: v4l2_rect_set_min_size(compose, &min_rect);
964: v4l2_rect_set_max_size(compose, &max_rect);
965: }
966: v4l2_rect_map_inside(compose, &fmt);
967: dev->fmt_cap_rect = fmt;
968: tpg_s_buf_height(&dev->tpg, fmt.height);
969: } else if (dev->has_compose_cap) {
970: struct v4l2_rect fmt = dev->fmt_cap_rect;
971:
972: v4l2_rect_set_min_size(&fmt, &s->r);
973: if (!v4l2_rect_same_size(&dev->fmt_cap_rect, &fmt) &&
974: vb2_is_busy(&dev->vb_vid_cap_q))
975: return -EBUSY;
976: dev->fmt_cap_rect = fmt;
977: tpg_s_buf_height(&dev->tpg, fmt.height);
978: v4l2_rect_set_size_to(compose, &s->r);
979: v4l2_rect_map_inside(compose, &dev->fmt_cap_rect);
]
|
| 80/2 |
2026/07/17 00:54 |
llm |
expert |
1m
Model:
Tokens:
input: 76287
output: 34
thoughts: 8207
Thoughts: **Analyzing the Image Width Discrepancy**
Okay, so I'm diving into this V4L2 driver code and trying to figure out how `img_width` can be 5120, while the buffer size allocated is only 4096, leading to this write-out-of-bounds issue. It's a classic case of the image stride being larger than what the buffer is set up for.
I'm starting by tracing how `img_width` and buffer sizes are determined, focusing on the `V4L2_SEL_TGT_CROP` and `V4L2_SEL_TGT_COMPOSE` selection targets, since those seem to be where the image dimensions get massaged. Initially, it's clear `compose` gets mapped inside `dev->fmt_cap_rect`, so `compose->width` is always less than or equal to `dev->fmt_cap_rect.width`. Also, `tpg->compose` is equal to `compose`, so anything applied to `compose` would be reflected in `tpg->compose`. This relationship is critical, and the initial checks show these conditions being enforced correctly.
Then I am thinking about how `tpg_s_crop_compose` maps `tpg->compose` to the cropped image. At the end of that call, the width for `tpg->compose` is fixed. I am also checking `tpg_fill_plane_buffer` where the problem might arise: `params.img_width = tpg_hdiv(tpg, p, tpg->compose.width)`. The calculated `img_width` must be SMALLER than the allocated `bytesperline`. But something's going wrong.
The critical piece seems to be the relationship between `img_width`, which I can see is determined by `tpg_hdiv`, and the `bytesperline`, which is determined using `tpg_g_bytesperline`. I have to figure out if there's any scenario where `tpg_hdiv` could give us a larger value than what's allocated. After verifying the data path and checking all the conditions, I am sure of one thing: The buffer size is calculated based on the stride and must be sufficient.
The issue, I think, lies in how the buffer is requested. The `vid_cap_queue_setup` and `vid_cap_queue_setup` are the interesting places where buffer sizes are actually determined. It's using `tpg_g_line_width` to calculate buffer sizes. If `tpg_g_line_width` is small, it leads to small `sizes[p]`. It then calls `vb2_vmalloc_alloc`. If `sizes[p]` is less than required, it returns -EINVAL. It seems impossible to get to a case where a too small buffer is allocated.
After some head scratching, I zero in on this: The bug is a write of size 5120 to an address that's only part of a 4096 byte allocation! Now the question is how did the program go there, I need to check the exact function that allocated the memory. And it's `vb2_vmalloc_alloc`, which is called with `sizes[p]`.
Then it hits me! I'm chasing the wrong variable. How CAN we get a small buffer and a large `img_width`? If we get `tpg->compose.width = 5120`, and `dev->fmt_cap_rect.width = 4096` then we can have this bug, but I have already shown that `tpg->compose.width` is always smaller. BUT WAIT! What if the user is providing the size? The code has a check, but it uses `tpg_g_line_width`. It still seems impossible!
I realize I have to work backward from the problem. The error is a write-out-of-bounds, suggesting the program is writing past the end of the allocated buffer. I know where the allocation occurs and that it's using the size given to it by the driver, so there's an issue with one of those values or calculations. My only lead: `img_width` is 5120, and `bytesperline` (aka the buffer size) is 4096.
This is a head-scratcher. It's like I have to find a logical contradiction in the code, or a condition that's not being properly handled. The relationship between `img_width`, `bytesperline` and `mp->width` is critical. If `mp->width` is small (4096), there has to be something that makes `bytesperline` small
|
| 81/2 |
2026/07/17 00:55 |
tool |
grepper |
0m
Args: map[Expression:compose_cap PathPrefix:drivers/media/test-drivers/vivid/]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-core.c=939=static int vivid_detect_feature_set(struct vivid_dev *dev, int inst,
--
drivers/media/test-drivers/vivid/vivid-core.c-1088- dev->has_crop_cap = *ccs_cap & 1;
drivers/media/test-drivers/vivid/vivid-core.c:1089: dev->has_compose_cap = *ccs_cap & 2;
drivers/media/test-drivers/vivid/vivid-core.c-1090- dev->has_scaler_cap = *ccs_cap & 4;
--
drivers/media/test-drivers/vivid/vivid-core.c-1092- dev->has_crop_cap ? 'Y' : 'N',
drivers/media/test-drivers/vivid/vivid-core.c:1093: dev->has_compose_cap ? 'Y' : 'N',
drivers/media/test-drivers/vivid/vivid-core.c-1094- dev->has_scaler_cap ? 'Y' : 'N');
--
drivers/media/test-drivers/vivid/vivid-core.h=207=struct vivid_dev {
--
drivers/media/test-drivers/vivid/vivid-core.h-348- struct v4l2_ctrl *ctrl_has_crop_cap;
drivers/media/test-drivers/vivid/vivid-core.h:349: struct v4l2_ctrl *ctrl_has_compose_cap;
drivers/media/test-drivers/vivid/vivid-core.h-350- struct v4l2_ctrl *ctrl_has_scaler_cap;
--
drivers/media/test-drivers/vivid/vivid-core.h-495- struct v4l2_rect crop_cap;
drivers/media/test-drivers/vivid/vivid-core.h:496: struct v4l2_rect compose_cap;
drivers/media/test-drivers/vivid/vivid-core.h-497- struct v4l2_rect crop_bounds_cap;
--
drivers/media/test-drivers/vivid/vivid-core.h-611- bool has_crop_cap;
drivers/media/test-drivers/vivid/vivid-core.h:612: bool has_compose_cap;
drivers/media/test-drivers/vivid/vivid-core.h-613- bool has_scaler_cap;
--
drivers/media/test-drivers/vivid/vivid-ctrls.c=506=static int vivid_vid_cap_s_ctrl(struct v4l2_ctrl *ctrl)
--
drivers/media/test-drivers/vivid/vivid-ctrls.c-623- return -EBUSY;
drivers/media/test-drivers/vivid/vivid-ctrls.c:624: dev->has_compose_cap = ctrl->val;
drivers/media/test-drivers/vivid/vivid-ctrls.c-625- vivid_update_format_cap(dev, true);
--
drivers/media/test-drivers/vivid/vivid-ctrls.c=876=static const struct v4l2_ctrl_config vivid_ctrl_has_crop_cap = {
--
drivers/media/test-drivers/vivid/vivid-ctrls.c-885-
drivers/media/test-drivers/vivid/vivid-ctrls.c:886:static const struct v4l2_ctrl_config vivid_ctrl_has_compose_cap = {
drivers/media/test-drivers/vivid/vivid-ctrls.c-887- .ops = &vivid_vid_cap_ctrl_ops,
--
drivers/media/test-drivers/vivid/vivid-ctrls.c=1631=int vivid_create_controls(struct vivid_dev *dev, bool show_ccs_cap,
--
drivers/media/test-drivers/vivid/vivid-ctrls.c-1813- &vivid_ctrl_has_crop_cap, NULL);
drivers/media/test-drivers/vivid/vivid-ctrls.c:1814: dev->ctrl_has_compose_cap = v4l2_ctrl_new_custom(hdl_vid_cap,
drivers/media/test-drivers/vivid/vivid-ctrls.c:1815: &vivid_ctrl_has_compose_cap, NULL);
drivers/media/test-drivers/vivid/vivid-ctrls.c-1816- dev->ctrl_has_scaler_cap = v4l2_ctrl_new_custom(hdl_vid_cap,
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c=92=static void scale_line(const u8 *src, u8 *dst, unsigned srcw, unsigned dstw, unsigned twopixsize)
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-125- * cropped on the capture side by crop_cap and scaled again to the video
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:126: * capture buffer using compose_cap.
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-127- *
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c=145=static void vivid_precalc_copy_rects(struct vivid_dev *dev, struct vivid_dev *out_dev)
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-164- dev->loop_vid_cap = dev->loop_vid_copy;
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:165: v4l2_rect_scale(&dev->loop_vid_cap, &dev->crop_cap, &dev->compose_cap);
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-166-
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-189- dev->loop_vid_overlay_cap = dev->loop_vid_overlay;
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:190: v4l2_rect_scale(&dev->loop_vid_overlay_cap, &dev->crop_cap, &dev->compose_cap);
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-191-
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c=216=static noinline_for_stack int vivid_copy_buffer(struct vivid_dev *dev,
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-224- unsigned twopixsize = tpg_g_twopixelsize(tpg, p);
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:225: unsigned img_width = tpg_hdiv(tpg, p, dev->compose_cap.width);
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:226: unsigned img_height = dev->compose_cap.height;
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-227- unsigned stride_cap = tpg->bytesperline[p];
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-264- (dev->loop_vid_out.top / vdiv) * stride_out;
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:265: vcapbuf += tpg_hdiv(tpg, p, dev->compose_cap.left) +
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:266: (dev->compose_cap.top / vdiv) * stride_cap;
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-267-
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c=805=static void vivid_grab_controls(struct vivid_dev *dev, bool grab)
--
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-807- v4l2_ctrl_grab(dev->ctrl_has_crop_cap, grab);
drivers/media/test-drivers/vivid/vivid-kthread-cap.c:808: v4l2_ctrl_grab(dev->ctrl_has_compose_cap, grab);
drivers/media/test-drivers/vivid/vivid-kthread-cap.c-809- v4l2_ctrl_grab(dev->ctrl_has_scaler_cap, grab);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=389=void vivid_update_format_cap(struct vivid_dev *dev, bool keep_controls)
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-455- dev->crop_bounds_cap = dev->src_rect;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:456: dev->compose_cap = dev->crop_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-457- if (V4L2_FIELD_HAS_T_OR_B(dev->field_cap))
drivers/media/test-drivers/vivid/vivid-vid-cap.c:458: dev->compose_cap.height /= 2;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:459: dev->fmt_cap_rect = dev->compose_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-460- tpg_s_video_aspect(&dev->tpg, vivid_get_video_aspect(dev));
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=564=int vivid_try_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-603- if (vivid_is_webcam(dev) ||
drivers/media/test-drivers/vivid/vivid-vid-cap.c:604: (!dev->has_scaler_cap && !dev->has_crop_cap && !dev->has_compose_cap)) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-605- mp->width = w;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-611- v4l2_rect_set_max_size(&r, &vivid_max_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:612: if (dev->has_scaler_cap && !dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-613- struct v4l2_rect max_r = { 0, 0, MAX_ZOOM * w, MAX_ZOOM * h };
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-615- v4l2_rect_set_max_size(&r, &max_r);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:616: } else if (!dev->has_scaler_cap && dev->has_crop_cap && !dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-617- v4l2_rect_set_max_size(&r, &dev->src_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=677=int vivid_s_fmt_vid_cap(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-682- struct v4l2_rect *crop = &dev->crop_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:683: struct v4l2_rect *compose = &dev->compose_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-684- struct vb2_queue *q = &dev->vb_vid_cap_q;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-704- if (!vivid_is_webcam(dev) &&
drivers/media/test-drivers/vivid/vivid-vid-cap.c:705: (dev->has_scaler_cap || dev->has_crop_cap || dev->has_compose_cap)) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-706- struct v4l2_rect r = { 0, 0, mp->width, mp->height };
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-708- if (dev->has_scaler_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c:709: if (dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-710- v4l2_rect_map_inside(compose, &r);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-712- *compose = r;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:713: if (dev->has_crop_cap && !dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-714- struct v4l2_rect min_r = {
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-743- }
drivers/media/test-drivers/vivid/vivid-vid-cap.c:744: } else if (dev->has_crop_cap && !dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-745- r.height *= factor;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-794- tpg_s_field(&dev->tpg, dev->field_cap, false);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:795: tpg_s_crop_compose(&dev->tpg, &dev->crop_cap, &dev->compose_cap);
drivers/media/test-drivers/vivid/vivid-vid-cap.c-796- if (vivid_is_sdtv_cap(dev))
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=870=int vivid_vid_cap_g_selection(struct file *file, void *priv,
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-874-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:875: if (!dev->has_crop_cap && !dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-876- return -ENOTTY;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-895- case V4L2_SEL_TGT_COMPOSE_BOUNDS:
drivers/media/test-drivers/vivid/vivid-vid-cap.c:896: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-897- return -EINVAL;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-900- case V4L2_SEL_TGT_COMPOSE:
drivers/media/test-drivers/vivid/vivid-vid-cap.c:901: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-902- return -EINVAL;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:903: sel->r = dev->compose_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-904- break;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-905- case V4L2_SEL_TGT_COMPOSE_DEFAULT:
drivers/media/test-drivers/vivid/vivid-vid-cap.c:906: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-907- return -EINVAL;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c=916=int vivid_vid_cap_s_selection(struct file *file, void *priv, struct v4l2_selection *s)
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-919- struct v4l2_rect *crop = &dev->crop_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:920: struct v4l2_rect *compose = &dev->compose_cap;
drivers/media/test-drivers/vivid/vivid-vid-cap.c-921- unsigned factor = V4L2_FIELD_HAS_T_OR_B(dev->field_cap) ? 2 : 1;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-923-
drivers/media/test-drivers/vivid/vivid-vid-cap.c:924: if (!dev->has_crop_cap && !dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-925- return -ENOTTY;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-956- v4l2_rect_set_min_size(&fmt, &min_rect);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:957: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-958- v4l2_rect_set_max_size(&fmt, &max_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-961- return -EBUSY;
drivers/media/test-drivers/vivid/vivid-vid-cap.c:962: if (dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-963- v4l2_rect_set_min_size(compose, &min_rect);
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-968- tpg_s_buf_height(&dev->tpg, fmt.height);
drivers/media/test-drivers/vivid/vivid-vid-cap.c:969: } else if (dev->has_compose_cap) {
drivers/media/test-drivers/vivid/vivid-vid-cap.c-970- struct v4l2_rect fmt = dev->fmt_cap_rect;
--
drivers/media/test-drivers/vivid/vivid-vid-cap.c-993- case V4L2_SEL_TGT_COMPOSE:
drivers/media/test-drivers/vivid/vivid-vid-cap.c:994: if (!dev->has_compose_cap)
drivers/media/test-drivers/vivid/vivid-vid-cap.c-995- return -EINVAL;
]
|
| 82/2 |
2026/07/17 00:55 |
llm |
expert |
0m
Model:
Tokens:
input: 90778
output: 42
thoughts: 2671
Thoughts: **Analyzing Capture Buffer Size Mismatch**
Okay, here's my thought process on this capture buffer issue. I'm focusing on why a buffer size of 4096 bytes is reported when it *should* be much larger, given a specified image width of 5120 pixels.
First, I'm zeroing in on the `vivid_vid_cap_s_selection` function, specifically how it handles crop selections (`V4L2_SEL_TGT_CROP`). The code modifies a rectangle called `compose`, which represents the region of the image being composed, which will ultimately get mapped into the target image. It does this while taking into account whether scaler and/or compose capabilities are enabled. Regardless of whether scaling/composing is supported the code ensures that `compose` fits inside the `dev->fmt_cap_rect`, which represents the current capture format rectangle. Importantly, the code checks for buffer allocation (using `vb2_is_busy`) and returns an error (`-EBUSY`) if the `fmt_cap_rect` is changed *while* buffers are allocated. This is a critical check since the code relies on the size of the capture format rectangle remaining constant while buffers are allocated.
This then leads me to `vivid_s_fmt_vid_cap`. I see the `fmt_cap_rect` is set to `r`, where `r`'s width and height is initialized with the user provided values from `mp->width` and `mp->height`. Then I trace `tpg->compose.width`, and the calculation of `tpg->bytesperline`, which is a function of `mp->width` and `bit_depth`. The code should ensure the actual image width (`img_width`) is bounded by `bytesperline`, which, based on the calculation, should not be smaller than the provided buffer size given `mp->width` and `bit_depth`.
I then dig into the `vid_cap_queue_setup` and examine how it uses `tpg_g_line_width` to determine a required size and checks against the buffer sizes passed in via `VIDIOC_CREATE_BUFS`. I realize the user can specify the sizes. The checks verify that the user specified sizes are big enough. If not, it returns `-EINVAL`. I'm trying to find a situation where it would accept a small size, but the calculations are not cooperating.
The issue hinges on how `tpg_g_line_width` gets its values. I see that it uses `dev->fmt_cap_rect.height` for height. The minimum size for height is derived in `vivid_try_fmt_vid_cap`. I confirm that the height is at least 16.
My next line of inquiry then follows `tpg_g_line_width`. I go through the `vivid_s_fmt_vid_cap` function and follow the logic that calculates and sets the `bytesperline`. I see `tpg->bytesperline[p]` is set from user-provided values. I confirm the format setup with `tpg_s_fourcc`. I verify that `tpg->bytesperline[p]` is correctly initialized from the format parameters provided by the user.
Finally, I look for corner cases in the format structure `vivid_formats`. I re-examine if there are any formats with zero `bit_depth` values which could lead to small `bytesperline` values, but I don't see anything. I'm stumped - given how the code is structured, the buffer size should be large enough based on the calculations, yet it is not.
|
| 83/2 |
2026/07/17 00:56 |
tool |
grepper |
0m
Args: map[Expression:bit_depth PathPrefix:drivers/media/test-drivers/vivid/vivid-vid-common.c]
Results: map[Output:drivers/media/test-drivers/vivid/vivid-vid-common.c=34=struct vivid_fmt vivid_formats[] = {
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-37- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:38: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-39- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-46- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:47: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-48- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-54- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:55: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-56- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-62- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:63: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-64- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-70- .vdownsampling = { 1, 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:71: .bit_depth = { 8, 4, 4 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-72- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-78- .vdownsampling = { 1, 2, 2 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:79: .bit_depth = { 8, 4, 4 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-80- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-86- .vdownsampling = { 1, 2, 2 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:87: .bit_depth = { 8, 4, 4 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-88- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-94- .vdownsampling = { 1, 2 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:95: .bit_depth = { 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-96- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-102- .vdownsampling = { 1, 2 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:103: .bit_depth = { 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-104- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-110- .vdownsampling = { 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:111: .bit_depth = { 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-112- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-118- .vdownsampling = { 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:119: .bit_depth = { 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-120- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-126- .vdownsampling = { 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:127: .bit_depth = { 8, 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-128- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-134- .vdownsampling = { 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:135: .bit_depth = { 8, 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-136- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-142- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:143: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-144- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-150- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:151: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-152- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-157- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:158: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-159- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-165- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:166: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-167- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-173- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:174: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-175- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-181- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:182: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-183- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-188- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:189: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-190- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-196- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:197: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-198- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-203- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:204: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-205- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-211- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:212: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-213- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-218- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:219: .bit_depth = { 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-220- .color_enc = TGP_COLOR_ENC_LUMA,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-226- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:227: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-228- .color_enc = TGP_COLOR_ENC_LUMA,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-234- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:235: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-236- .color_enc = TGP_COLOR_ENC_LUMA,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-242- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:243: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-244- .color_enc = TGP_COLOR_ENC_LUMA,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-250- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:251: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-252- .color_enc = TGP_COLOR_ENC_LUMA,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-258- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:259: .bit_depth = { 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-260- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-265- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:266: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-267- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-273- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:274: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-275- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-281- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:282: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-283- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-288- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:289: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-290- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-295- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:296: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-297- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-303- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:304: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-305- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-310- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:311: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-312- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-318- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:319: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-320- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-325- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:326: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-327- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-333- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:334: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-335- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-340- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:341: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-342- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-348- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:349: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-350- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-356- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:357: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-358- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-364- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:365: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-366- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-373- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:374: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-375- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-381- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:382: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-383- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-390- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:391: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-392- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-398- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:399: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-400- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-407- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:408: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-409- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-415- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:416: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-417- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-424- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:425: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-426- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-431- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:432: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-433- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-438- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:439: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-440- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-446- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:447: .bit_depth = { 24 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-448- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-453- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:454: .bit_depth = { 24 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-455- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-460- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:461: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-462- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-467- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:468: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-469- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-474- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:475: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-476- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-481- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:482: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-483- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-488- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:489: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-490- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-495- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:496: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-497- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-503- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:504: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-505- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-511- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:512: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-513- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-518- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:519: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-520- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-525- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:526: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-527- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-533- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:534: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-535- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-541- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:542: .bit_depth = { 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-543- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-548- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:549: .bit_depth = { 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-550- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-555- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:556: .bit_depth = { 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-557- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-562- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:563: .bit_depth = { 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-564- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-569- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:570: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-571- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-576- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:577: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-578- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-583- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:584: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-585- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-590- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:591: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-592- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-597- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:598: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-599- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-604- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:605: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-606- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-611- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:612: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-613- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-618- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:619: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-620- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-625- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:626: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-627- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-632- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:633: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-634- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-639- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:640: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-641- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-646- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:647: .bit_depth = { 16 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-648- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-654- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:655: .bit_depth = { 24 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-656- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-662- .vdownsampling = { 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:663: .bit_depth = { 32 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-664- .planes = 1,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-672- .vdownsampling = { 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:673: .bit_depth = { 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-674- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-681- .vdownsampling = { 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:682: .bit_depth = { 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-683- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-690- .vdownsampling = { 1, 2, 2 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:691: .bit_depth = { 8, 4, 4 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-692- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-698- .vdownsampling = { 1, 2, 2 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:699: .bit_depth = { 8, 4, 4 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-700- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-706- .vdownsampling = { 1, 2 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:707: .bit_depth = { 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-708- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-714- .vdownsampling = { 1, 2 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:715: .bit_depth = { 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-716- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-722- .vdownsampling = { 1, 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:723: .bit_depth = { 8, 4, 4 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-724- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-730- .vdownsampling = { 1, 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:731: .bit_depth = { 8, 4, 4 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-732- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-738- .vdownsampling = { 1, 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:739: .bit_depth = { 8, 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-740- .color_enc = TGP_COLOR_ENC_YCBCR,
--
drivers/media/test-drivers/vivid/vivid-vid-common.c-746- .vdownsampling = { 1, 1, 1 },
drivers/media/test-drivers/vivid/vivid-vid-common.c:747: .bit_depth = { 8, 8, 8 },
drivers/media/test-drivers/vivid/vivid-vid-common.c-748- .color_enc = TGP_COLOR_ENC_YCBCR,
]
|
| 84/2 |
2026/07/17 00:56 |
llm |
expert |
0m
Model:
Tokens:
input: 104550
output: 66
thoughts: 3695
Thoughts: **Analysis of a Vulnerability in the VIVID Video Driver**
Okay, let's break this down. Initially, the code establishes basic constraints: the bit depth, which dictates a minimum `bytesperline`, which in turn sets a lower bound on `sizeimage` and height. The initial calculations seem logical – small dimensions lead to a small buffer allocation by `vb2_vmalloc_alloc`. But then, the reported bug describes a scenario where `img_width` is very large (5120), yet the allocated buffer is small (4096 bytes). This seems mathematically impossible.
I started digging into where these variables are determined, focusing on how `img_width` could become so large despite the initial size constraints. The analysis led me to a potential issue in how `vivid_try_fmt_vid_cap` handles format changes. Specifically, I considered: could `mp->height`, `pfmt[p].bytesperline`, or `fmt->vdownsampling[p]` contribute to this discrepancy? However, the code contains checks that handle these parameters such that they wouldn't, on their own, cause the problem. Overflow seemed unlikely, too.
Then the key observation came: Multiplanar formats and the handling of the number of planes using the `fmt->buffers` and `fmt->planes` in the `vivid_try_fmt_vid_cap` function didn't seem to be the cause.
The breakthrough came when examining `VIDIOC_S_SELECTION`. This ioctl is the culprit. When `VIDIOC_S_SELECTION` with `V4L2_SEL_TGT_CROP` is used the code can manipulate `dev->fmt_cap_rect` to change the `compose` width. The crucial mistake, however, is that this ioctl *modifies* the "format size" (`dev->fmt_cap_rect` and `dev->compose_cap`) without re-calculating or updating the `bytesperline`, or the resulting buffer size (`sizeimage`).
Specifically, `vivid_vid_cap_s_selection` updates `dev->fmt_cap_rect` based on a cropping selection. However, it *doesn't* update `tpg->bytesperline[p]`. This means the `bytesperline` value used for buffer allocation is stale, while the calculated `compose->width` uses the new, larger, potentially unbounded `dev->fmt_cap_rect`. This inconsistency creates the out-of-bounds write: the driver calculates a smaller-than-necessary buffer size, but then attempts to write data with the new `compose->width`.
I devised a test case to reproduce the bug: First, set up a small format. Then, use `VIDIOC_S_SELECTION` to set a much larger crop rectangle. Subsequent `VIDIOC_REQBUFS` calls will allocate a buffer with the "old" (small) `bytesperline`, but the streaming operation will use the new large cropping width to fill the buffer. This confirms the out-of-bounds write is reachable.
Now, is this exploitable? Considering this is a "test" driver, normally not loaded, I would normally consider it non-exploitable for a standard production build. However, assuming an attacker *somehow* manages to have the module loaded, any user with access to the `/dev/videoX` device can trigger the bug. While the driver writes a test pattern, the out-of-bounds write in `vmalloc` can corrupt adjacent memory regions, leading to a kernel crash (Denial of Service). This bug is thus exploitable because it's a controlled out-of-bounds write, potentially corrupting kernel memory. Although access to `/dev/videoX` would typically require group membership or ACLs, for the purposes of a test driver it *is* accessible, but it would require an explicit configuration change in the build, the load the module. And for a typical system, users might not have loaded test drivers. Therefore, this bug can only be exploited with an explicit build configuration. This bug is a denial of service. It is exploitable under this condition.
|
| 85/2 |
2026/07/17 00:56 |
tool |
set-results |
0m
Args: map[DenialOfService:true Exploitable:true FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
Results: map[DenialOfService:true Exploitable:true FilesystemTrigger:false NetworkTrigger:false PeripheralTrigger:false RemoteTrigger:false Unprivileged:false UserNamespace:false VMGuestTrigger:false VMHostTrigger:false]
|
| 86/2 |
2026/07/17 00:56 |
llm |
expert |
0m
Model:
Tokens:
input: 109255
output: 572
thoughts: 413
Thoughts: **My Analysis of the Vivid Driver Vulnerability**
Okay, so I've got this vivid test driver bug, specifically a vmalloc out-of-bounds write. Digging in, the root of the problem seems to be the way `VIDIOC_S_SELECTION` handles the dimensions of the capture and compose rectangles. It's capable of changing `dev->fmt_cap_rect` and `dev->compose_cap` without properly updating `bytesperline`, or stride, for the image planes. That's where the trouble begins.
Think about it. We first set up our format, maybe with a tiny resolution like 16x16 using `VIDIOC_S_FMT`. The driver happily calculates a small `bytesperline`, then later when `VIDIOC_REQBUFS` is called, it uses that small stride to allocate the buffer. Makes sense so far, small resolution, small buffer.
But then, we come along and use `VIDIOC_S_SELECTION` to enlarge those compose dimensions. Now the interesting part. During streaming, `tpg_fill_plane_buffer` uses that *enlarged* `compose.width` to calculate `img_width` – the actual number of bytes to write per line. The `bytesperline` that was used for buffer allocation is still small and is not reflecting the new size! The result? `img_width` becomes much *larger* than `bytesperline`.
This is where the vulnerability becomes clear. The `memcpy` in `tpg_fill_plane_buffer` is now going to write past the end of that small, allocated vmalloc buffer because the write size is far larger than the buffer size. We're talking about a classic out-of-bounds write, a memory corruption in vmalloc space.
From a security standpoint, this is concerning. Since it's a vmalloc OOB write, the implications are privilege escalation and Denial of Service. However, it's not quite as critical as it could be. This is the `vivid` driver, which is a virtual test driver, and not intended for production systems. It's disabled by default, doesn't auto-load, and access to the `/dev/videoX` devices is usually tightly restricted. So, even though exploitable in theory, the attack surface in a typical production environment is limited. Nevertheless, it does highlight the importance of careful dimension management within the V4L2 framework.
|
| 87/1 |
2026/07/17 00:57 |
action |
format-explanation |
0m
Results: map[Explanation:**Analysis:**
The bug is a `vmalloc` out-of-bounds write in the `vivid` V4L2 test driver
(`drivers/media/test-drivers/vivid/`).
**Root Cause:**
The issue stems from a mismatch between the buffer size calculation and the
image width used during rendering.
1. A user can call `VIDIOC_S_FMT` to set a very small format resolution (e.g.,
16x16). This sets a correspondingly small `bytesperline` (stride) for the image
planes.
2. The user then calls `VIDIOC_S_SELECTION` (with `V4L2_SEL_TGT_CROP` or
`V4L2_SEL_TGT_COMPOSE`) to set a much larger crop/compose rectangle (e.g., 4096
width). The driver updates `dev->fmt_cap_rect` and `dev->compose_cap` to this
larger size but **fails to update `bytesperline`** to accommodate the new width.
3. When `VIDIOC_REQBUFS` is called to allocate buffers, `vid_cap_queue_setup()`
calculates the required buffer size based on the small `bytesperline`. This
results in a small `vmalloc` allocation (e.g., 1 page / 4096 bytes).
4. During streaming, the test pattern generator (`tpg_fill_plane_buffer`)
calculates the number of bytes to write per line (`img_width`) based on the
enlarged `compose.width`.
5. This results in `memcpy()` writing a large amount of data (e.g., 5120 bytes)
into the small allocated buffer (4096 bytes), causing a `vmalloc` out-of-bounds
write.
**Security Impact:**
- **Exploitable & Denial of Service:** The bug allows an attacker to perform an
out-of-bounds write in `vmalloc` memory with a controlled size. This memory
corruption can be leveraged to corrupt adjacent `vmalloc` allocations,
potentially leading to privilege escalation or a kernel panic (Denial of
Service).
- **Unprivileged Access:** The `vivid` driver is a virtual test driver
(`CONFIG_VIDEO_VIVID`). It is not enabled in production kernels, nor is it
auto-loaded by the kernel since it lacks hardware IDs. Furthermore, even if it
were manually loaded, access to `/dev/videoX` nodes is typically restricted to
the `video` group or local logged-in users via ACLs. Therefore, this bug is not
reachable by a typical unprivileged process on a standard production system.]
|