KASAN: slab-use-after-free Read in dvb_frontend_release

Status: upstream: reported C repro on 2026/02/09 03:58
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+c7c57465f74219389dc6@syzkaller.appspotmail.com
First crash: 235d, last: 13h45m
Fix bisection: failed (error log, bisect log)
  
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/05/28 upstream (ToT) 8fde5d1d47f6 C [report] KASAN: slab-use-after-free Read in dvb_frontend_release
▶ ▼ Similar bugs (5)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in dvb_frontend_release (2) media 19 3 405d 401d 0/29 auto-obsoleted due to no activity on 2025/11/21 10:00
upstream KASAN: slab-use-after-free Read in dvb_frontend_release media 19 2 529d 538d 0/29 auto-obsoleted due to no activity on 2025/07/20 03:14
upstream KASAN: slab-use-after-free Read in dvb_frontend_release (3) prio:high media 19 syz, C error 328 2h17m 229d 0/29 upstream: reported C repro on 2026/02/14 12:34
linux-5.15 KASAN: use-after-free Read in dvb_frontend_release origin:upstream 19 syz, C error 6 61d 213d 0/3 upstream: reported C repro on 2026/03/02 23:20
linux-6.1 KASAN: use-after-free Read in dvb_frontend_release origin:lts-only 19 syz, C error 14 88d 206d 0/3 upstream: reported C repro on 2026/03/09 12:55

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in dvb_frontend_release+0x3fc/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2921
Read of size 4 at addr ffff888142a5363c by task syz.0.18/5944

CPU: 1 PID: 5944 Comm: syz.0.18 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xa8/0x210 mm/kasan/report.c:468
 kasan_report+0x117/0x150 mm/kasan/report.c:581
 dvb_frontend_release+0x3fc/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2921
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:180
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:213
 __syscall_exit_to_user_mode_work kernel/entry/common.c:294 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:305
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7fcc30f9e159
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffea773bff8 EFLAGS: 00000246 ORIG_RAX: 00000000000001b4
RAX: 0000000000000000 RBX: 00007ffea773c0e0 RCX: 00007fcc30f9e159
RDX: 0000000000000000 RSI: 000000000000001e RDI: 0000000000000003
RBP: 000000000001f73a R08: 0000000000000001 R09: 0000000000000000
R10: 0000001b2ce20000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fcc31225fac R14: 00007fcc31225fa8 R15: 00007fcc31225fa0
 </TASK>

Allocated by task 1:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:384
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 dvb_register_device+0x309/0x1df0 drivers/media/dvb-core/dvbdev.c:475
 dvb_register_frontend+0x62d/0x900 drivers/media/dvb-core/dvb_frontend.c:3056
 vidtv_bridge_dvb_init drivers/media/test-drivers/vidtv/vidtv_bridge.c:438 [inline]
 vidtv_bridge_probe+0x9d6/0xf60 drivers/media/test-drivers/vidtv/vidtv_bridge.c:510
 platform_probe+0x13b/0x1c0 drivers/base/platform.c:1376
 call_driver_probe drivers/base/dd.c:-1 [inline]
 really_probe+0x247/0xae0 drivers/base/dd.c:717
 __driver_probe_device+0x1f5/0x390 drivers/base/dd.c:879
 driver_probe_device+0x4f/0x420 drivers/base/dd.c:909
 __driver_attach+0x444/0x6d0 drivers/base/dd.c:1295
 bus_for_each_dev+0x235/0x2b0 drivers/base/bus.c:370
 bus_add_driver+0x340/0x630 drivers/base/bus.c:723
 driver_register+0x23a/0x310 drivers/base/driver.c:246
 vidtv_bridge_init+0x49/0x80 drivers/media/test-drivers/vidtv/vidtv_bridge.c:602
 do_one_initcall+0x242/0x790 init/main.c:1210
 do_initcall_level+0x13d/0x1f0 init/main.c:1272
 do_initcalls+0x69/0xd0 init/main.c:1288
 kernel_init_freeable+0x3d9/0x560 init/main.c:1525
 kernel_init+0x1d/0x1c0 init/main.c:1415
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

Freed by task 5944:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x28/0x40 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1f0 mm/kasan/common.c:237
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1811 [inline]
 slab_free_freelist_hook+0x130/0x1a0 mm/slub.c:1837
 slab_free mm/slub.c:3830 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3843
 dvb_free_device drivers/media/dvb-core/dvbdev.c:619 [inline]
 kref_put include/linux/kref.h:65 [inline]
 dvb_device_put drivers/media/dvb-core/dvbdev.c:632 [inline]
 dvb_generic_release+0x123/0x1b0 drivers/media/dvb-core/dvbdev.c:169
 dvb_frontend_release+0x138/0x4a0 drivers/media/dvb-core/dvb_frontend.c:2919
 __fput+0x221/0x940 fs/file_table.c:418
 task_work_run+0x1d4/0x260 kernel/task_work.c:245
 resume_user_mode_work include/linux/resume_user_mode.h:49 [inline]
 exit_to_user_mode_loop+0xe6/0x110 kernel/entry/common.c:180
 exit_to_user_mode_prepare+0xee/0x180 kernel/entry/common.c:213
 __syscall_exit_to_user_mode_work kernel/entry/common.c:294 [inline]
 syscall_exit_to_user_mode+0x1a/0x50 kernel/entry/common.c:305
 do_syscall_64+0x61/0xb0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x68/0xd2

The buggy address belongs to the object at ffff888142a53600
 which belongs to the cache kmalloc-256 of size 256
The buggy address is located 60 bytes inside of
 freed 256-byte region [ffff888142a53600, ffff888142a53700)

The buggy address belongs to the physical page:
page:ffffea00050a9480 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x142a52
head:ffffea00050a9480 order:1 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x57ff00000000840(slab|head|node=1|zone=2|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 057ff00000000840 ffff888017c41b40 dead000000000122 0000000000000000
raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 1, migratetype Unmovable, gfp_mask 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 1, tgid 1 (swapper/0), ts 18513351207, free_ts 0
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1582
 prep_new_page mm/page_alloc.c:1589 [inline]
 get_page_from_freelist+0x2181/0x22a0 mm/page_alloc.c:3221
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4501
 alloc_page_interleave+0x24/0x1e0 mm/mempolicy.c:2118
 alloc_slab_page+0x5d/0x180 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5c/0x12f0 mm/slub.c:3253
 __slab_alloc mm/slub.c:3339 [inline]
 __slab_alloc_node mm/slub.c:3392 [inline]
 slab_alloc_node mm/slub.c:3485 [inline]
 __kmem_cache_alloc_node+0x11f/0x250 mm/slub.c:3534
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 kzalloc include/linux/slab.h:721 [inline]
 bus_add_driver+0x162/0x630 drivers/base/bus.c:707
 driver_register+0x23a/0x310 drivers/base/driver.c:246
 usb_register_driver+0x1aa/0x360 drivers/usb/core/driver.c:1064
 do_one_initcall+0x242/0x790 init/main.c:1210
 do_initcall_level+0x13d/0x1f0 init/main.c:1272
 do_initcalls+0x69/0xd0 init/main.c:1288
 kernel_init_freeable+0x3d9/0x560 init/main.c:1525
page_owner free stack trace missing

Memory state around the buggy address:
 ffff888142a53500: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff888142a53580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff888142a53600: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff888142a53680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888142a53700: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (8):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/10/01 21:47 linux-6.6.y 79643295eba1 f5cdae2f .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/05/27 09:38 linux-6.6.y 0a40c6fbd105 2b01f00e .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/02/09 03:58 linux-6.6.y c56aaf1a85ae 4c131dc4 .config console log report syz / log [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/10/01 15:36 linux-6.6.y 79643295eba1 f5cdae2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/09/30 13:26 linux-6.6.y 79643295eba1 7808aef4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/05/27 00:47 linux-6.6.y 0a40c6fbd105 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/05/27 00:47 linux-6.6.y 0a40c6fbd105 2b01f00e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in dvb_frontend_release
2026/09/30 13:25 linux-6.6.y 79643295eba1 7808aef4 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KFENCE: use-after-free read in dvb_frontend_release
* Struck through repros no longer work on HEAD.