KASAN: slab-out-of-bounds Read in __dynamic_dev_dbg

Status: upstream: reported C repro on 2026/09/18 17:57
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+6083aab9c72288acd851@syzkaller.appspotmail.com
First crash: 47d, last: 34d
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/10/28 upstream (ToT) 65ba8f34ec88 C [report] KASAN: slab-out-of-bounds Read in __dynamic_dev_dbg
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in __dynamic_dev_dbg prio:normal driver-core media 19 syz, C 560 4h13m 49d 26/29 upstream: reported C repro on 2026/09/16 15:53
linux-5.15 KASAN: use-after-free Read in __dynamic_dev_dbg 19 5 6h57m 18d 0/3 upstream: reported on 2026/10/17 04:30
linux-6.6 general protection fault in __dynamic_dev_dbg 2 1 45d 45d 0/2 upstream: reported on 2026/09/21 02:53

Sample crash report:
==================================================================
BUG: KASAN: slab-out-of-bounds in hex_string+0x3a0/0x484 lib/vsprintf.c:1180
Read of size 1 at addr ffff0000cdf2457c by task syz.0.17/4534

CPU: 0 PID: 4534 Comm: syz.0.17 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/07/2026
Call trace:
 dump_backtrace+0x1c4/0x1f0 arch/arm64/kernel/stacktrace.c:158
 show_stack+0x2c/0x3c arch/arm64/kernel/stacktrace.c:165
 __dump_stack+0x30/0x40 lib/dump_stack.c:88
 dump_stack_lvl+0xf4/0x15c lib/dump_stack.c:106
 print_address_description+0x88/0x218 mm/kasan/report.c:316
 print_report+0x50/0x68 mm/kasan/report.c:420
 kasan_report+0xa8/0xfc mm/kasan/report.c:524
 __asan_report_load1_noabort+0x2c/0x38 mm/kasan/report_generic.c:348
 hex_string+0x3a0/0x484 lib/vsprintf.c:1180
 pointer+0x1cc/0xdd8 lib/vsprintf.c:2408
 vsnprintf+0xcc0/0x18d8 lib/vsprintf.c:2809
 va_format lib/vsprintf.c:1685 [inline]
 pointer+0x7ac/0xdd8 lib/vsprintf.c:2436
 vsnprintf+0xcc0/0x18d8 lib/vsprintf.c:2809
 vscnprintf+0x6c/0xd8 lib/vsprintf.c:2911
 printk_sprint+0xc0/0x638 kernel/printk/printk.c:2124
 vprintk_store+0x72c/0xb60 kernel/printk/printk.c:2238
 vprintk_emit+0x118/0x2f0 kernel/printk/printk.c:2284
 dev_vprintk_emit+0x2dc/0x39c drivers/base/core.c:4948
 dev_printk_emit+0xe0/0x130 drivers/base/core.c:4959
 __dynamic_dev_dbg+0x1b4/0x250 lib/dynamic_debug.c:900
 dtv_property_process_get+0x2b0c/0x2c70 drivers/media/dvb-core/dvb_frontend.c:1592
 dvb_get_property drivers/media/dvb-core/dvb_frontend.c:2390 [inline]
 dvb_frontend_handle_ioctl drivers/media/dvb-core/dvb_frontend.c:2471 [inline]
 dvb_frontend_do_ioctl+0x1c20/0x34f8 drivers/media/dvb-core/dvb_frontend.c:2097
 dvb_usercopy+0x248/0x45c drivers/media/dvb-core/dvbdev.c:1007
 dvb_frontend_ioctl+0x68/0x8c drivers/media/dvb-core/dvb_frontend.c:2111
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

Allocated by task 4534:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4c/0x80 mm/kasan/common.c:53
 kasan_save_alloc_info+0x24/0x30 mm/kasan/generic.c:505
 ____kasan_kmalloc mm/kasan/common.c:375 [inline]
 __kasan_kmalloc+0xa0/0xb8 mm/kasan/common.c:384
 kasan_kmalloc include/linux/kasan.h:211 [inline]
 __do_kmalloc_node mm/slab_common.c:936 [inline]
 __kmalloc_node_track_caller+0xcc/0x174 mm/slab_common.c:956
 memdup_user+0x60/0x204 mm/util.c:174
 memdup_array_user include/linux/string.h:36 [inline]
 dvb_get_property drivers/media/dvb-core/dvb_frontend.c:2373 [inline]
 dvb_frontend_handle_ioctl drivers/media/dvb-core/dvb_frontend.c:2471 [inline]
 dvb_frontend_do_ioctl+0xd8c/0x34f8 drivers/media/dvb-core/dvb_frontend.c:2097
 dvb_usercopy+0x248/0x45c drivers/media/dvb-core/dvbdev.c:1007
 dvb_frontend_ioctl+0x68/0x8c drivers/media/dvb-core/dvb_frontend.c:2111
 vfs_ioctl fs/ioctl.c:51 [inline]
 __do_sys_ioctl fs/ioctl.c:870 [inline]
 __se_sys_ioctl fs/ioctl.c:856 [inline]
 __arm64_sys_ioctl+0x14c/0x1c8 fs/ioctl.c:856
 __invoke_syscall arch/arm64/kernel/syscall.c:38 [inline]
 invoke_syscall+0x98/0x290 arch/arm64/kernel/syscall.c:52
 el0_svc_common+0x13c/0x258 arch/arm64/kernel/syscall.c:140
 do_el0_svc+0x5c/0x134 arch/arm64/kernel/syscall.c:204
 el0_svc+0x58/0x128 arch/arm64/kernel/entry-common.c:637
 el0t_64_sync_handler+0x84/0xf0 arch/arm64/kernel/entry-common.c:655
 el0t_64_sync+0x18c/0x190 arch/arm64/kernel/entry.S:585

The buggy address belongs to the object at ffff0000cdf24400
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 380 bytes inside of
 512-byte region [ffff0000cdf24400, ffff0000cdf24600)

The buggy address belongs to the physical page:
page:000000003385ace3 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x10df24
head:000000003385ace3 order:2 compound_mapcount:0 compound_pincount:0
flags: 0x5ffc00000010200(slab|head|node=0|zone=2|lastcpupid=0x7ff)
raw: 05ffc00000010200 0000000000000000 dead000000000122 ffff0000c0002600
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff0000cdf24400: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff0000cdf24480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff0000cdf24500: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 04
                                                                ^
 ffff0000cdf24580: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff0000cdf24600: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
==================================================================

Crashes (7):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/09/18 22:08 linux-6.1.y 1a8763b93150 853b104b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_dev_dbg
2026/09/18 21:23 linux-6.1.y 1a8763b93150 853b104b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_dev_dbg
2026/09/18 20:31 linux-6.1.y 1a8763b93150 853b104b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_dev_dbg
2026/09/18 19:47 linux-6.1.y 1a8763b93150 853b104b .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_dev_dbg
2026/09/18 17:59 linux-6.1.y 1a8763b93150 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_dev_dbg
2026/09/18 17:56 linux-6.1.y 1a8763b93150 853b104b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan-arm64 KASAN: slab-out-of-bounds Read in __dynamic_dev_dbg
2026/10/01 15:23 linux-6.1.y 1a8763b93150 f5cdae2f .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-1-kasan KASAN: use-after-free Read in __dynamic_dev_dbg
* Struck through repros no longer work on HEAD.