KASAN: slab-use-after-free Read in v4l2_open

Status: upstream: reported C repro on 2026/05/14 00:02
Bug presence: origin:upstream
[Documentation on labels]
Reported-by: syzbot+ded30d55c26df5f29c48@syzkaller.appspotmail.com
First crash: 71d, last: 8d04h
▶ ▼ Bug presence (1)
Date Name Commit Repro Result
2026/07/10 upstream (ToT) d96fcfe1b7f9 C [report] KASAN: slab-use-after-free Read in v4l2_open
▶ ▼ Similar bugs (3)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: slab-use-after-free Read in v4l2_open prio:high usb media 19 C error 2450 2h18m 127d 0/29 upstream: reported C repro on 2026/03/19 07:21
linux-6.1 KASAN: use-after-free Read in v4l2_open origin:upstream 19 C 18 2d15h 50d 0/3 upstream: reported C repro on 2026/06/03 20:38
linux-5.15 KASAN: use-after-free Read in v4l2_open origin:upstream 19 C 40 4d04h 50d 0/3 upstream: reported C repro on 2026/06/03 16:24
▶ ▼ Fix bisection attempts (1)
Created Duration User Patch Repo Result
2026/07/12 17:51 3h24m bisect fix linux-6.6.y OK (0) job log log

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in v4l2_open+0x359/0x360 drivers/media/v4l2-core/v4l2-dev.c:432
Read of size 4 at addr ffff88807c2cc7e0 by task v4l_id/6286

CPU: 0 PID: 6286 Comm: v4l_id Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
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
 v4l2_open+0x359/0x360 drivers/media/v4l2-core/v4l2-dev.c:432
 chrdev_open+0x5cc/0x6a0 fs/char_dev.c:414
 do_dentry_open+0x8c6/0x1500 fs/open.c:929
 do_open fs/namei.c:3640 [inline]
 path_openat+0x27f1/0x3230 fs/namei.c:3797
 do_filp_open+0x1f5/0x430 fs/namei.c:3824
 do_sys_openat2+0x134/0x1d0 fs/open.c:1421
 do_sys_open fs/open.c:1436 [inline]
 __do_sys_openat fs/open.c:1452 [inline]
 __se_sys_openat fs/open.c:1447 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1447
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f89ba6a7407
Code: 48 89 fa 4c 89 df e8 38 aa 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5b> c3 0f 1f 80 00 00 00 00 83 e2 39 83 fa 08 75 de e8 23 ff ff ff
RSP: 002b:00007ffcc96afd20 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f89badb1880 RCX: 00007f89ba6a7407
RDX: 0000000000000000 RSI: 00007ffcc96b1f1b RDI: ffffffffffffff9c
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffcc96aff70 R14: 00007f89baf10000 R15: 00005562c5dd74d8
 </TASK>

Allocated by task 5883:
 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]
 em28xx_v4l2_init+0x10b/0x2e70 drivers/media/usb/em28xx/em28xx-video.c:2538
 em28xx_init_extension+0x11c/0x1b0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
 kthread+0x2fa/0x390 kernel/kthread.c:388
 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 5883:
 kasan_save_stack mm/kasan/common.c:46 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:53
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 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/0x1e0 mm/slub.c:3843
 em28xx_free_v4l2 drivers/media/usb/em28xx/em28xx-video.c:2118 [inline]
 kref_put include/linux/kref.h:65 [inline]
 em28xx_v4l2_init+0x1670/0x2e70 drivers/media/usb/em28xx/em28xx-video.c:2907
 em28xx_init_extension+0x11c/0x1b0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_one_work kernel/workqueue.c:2653 [inline]
 process_scheduled_works+0xa5d/0x15d0 kernel/workqueue.c:2730
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2811
 kthread+0x2fa/0x390 kernel/kthread.c:388
 ret_from_fork+0x48/0x80 arch/x86/kernel/process.c:152
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff88807c2cc000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 2016 bytes inside of
 freed 8192-byte region [ffff88807c2cc000, ffff88807c2ce000)

The buggy address belongs to the physical page:
page:ffffea0001f0b200 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7c2c8
head:ffffea0001f0b200 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888017c42280 ffffea0001e1cc00 dead000000000002
raw: 0000000000000000 0000000080020002 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 3, migratetype Unmovable, gfp_mask 0xd2040(__GFP_IO|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5504, tgid 5504 (rcS), ts 59838956057, free_ts 59837566329
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1c1/0x200 mm/page_alloc.c:1581
 prep_new_page mm/page_alloc.c:1588 [inline]
 get_page_from_freelist+0x1951/0x19e0 mm/page_alloc.c:3220
 __alloc_pages+0x1f0/0x460 mm/page_alloc.c:4500
 alloc_slab_page+0x5d/0x160 mm/slub.c:1881
 allocate_slab mm/slub.c:2028 [inline]
 new_slab+0x87/0x2d0 mm/slub.c:2081
 ___slab_alloc+0xc5d/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+0x19e/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]
 tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
 tomoyo_init_log+0x1114/0x1f50 security/tomoyo/audit.c:264
 tomoyo_supervisor+0x363/0x1170 security/tomoyo/common.c:2089
 tomoyo_audit_env_log security/tomoyo/environ.c:36 [inline]
 tomoyo_env_perm+0x152/0x1f0 security/tomoyo/environ.c:63
 tomoyo_environ security/tomoyo/domain.c:672 [inline]
 tomoyo_find_next_domain+0x1592/0x1a60 security/tomoyo/domain.c:881
 tomoyo_bprm_check_security+0x116/0x170 security/tomoyo/tomoyo.c:101
 security_bprm_check+0x62/0xa0 security/security.c:1104
 search_binary_handler fs/exec.c:1763 [inline]
 exec_binprm fs/exec.c:1817 [inline]
 bprm_execve+0xa6e/0x1700 fs/exec.c:1892
 do_execveat_common+0x51b/0x6c0 fs/exec.c:1998
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1181 [inline]
 free_unref_page_prepare+0x7b2/0x8c0 mm/page_alloc.c:2365
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2458
 discard_slab mm/slub.c:2127 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2667
 put_cpu_partial+0x17c/0x250 mm/slub.c:2743
 __slab_free+0x319/0x400 mm/slub.c:3700
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xd0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:306
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4b0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3495 [inline]
 __kmem_cache_alloc_node+0x13a/0x250 mm/slub.c:3534
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 kmalloc include/linux/slab.h:600 [inline]
 tomoyo_print_header security/tomoyo/audit.c:156 [inline]
 tomoyo_init_log+0x196/0x1f50 security/tomoyo/audit.c:255
 tomoyo_supervisor+0x363/0x1170 security/tomoyo/common.c:2089
 tomoyo_find_next_domain+0x44a/0x1a60 security/tomoyo/domain.c:755
 tomoyo_bprm_check_security+0x116/0x170 security/tomoyo/tomoyo.c:101
 security_bprm_check+0x62/0xa0 security/security.c:1104

Memory state around the buggy address:
 ffff88807c2cc680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807c2cc700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88807c2cc780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff88807c2cc800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807c2cc880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (5):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/05/14 14:44 linux-6.6.y 3b9f64db0496 6ccb967e .config console log report syz / log C [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in v4l2_open
2026/07/16 08:21 linux-6.6.y da47cbc25466 27a8bd60 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in v4l2_open
2026/06/11 23:45 linux-6.6.y 924b4a879cbb d93a6ab6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in v4l2_open
2026/06/03 18:44 linux-6.6.y 924b4a879cbb 234057e5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in v4l2_open
2026/05/14 00:02 linux-6.6.y 3b9f64db0496 6ccb967e .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in v4l2_open
* Struck through repros no longer work on HEAD.