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KASAN: slab-use-after-free Read in v4l2_fh_open

Status: upstream: reported on 2025/06/29 09:48
Reported-by: syzbot+a84875971de9f0c23595@syzkaller.appspotmail.com
First crash: 4d03h, last: 4d03h
▶ ▼ Similar bugs (3)
Kernel Title Repro Cause bisect Fix bisect Count Last Reported Patched Status
upstream KASAN: use-after-free Read in v4l2_fh_open usb media C unreliable inconclusive 1685 2h47m 1598d 0/29 upstream: reported C repro on 2021/02/15 15:18
linux-5.15 KASAN: use-after-free Read in v4l2_fh_open origin:upstream C 83 14h47m 336d 0/3 upstream: reported C repro on 2024/08/01 11:01
linux-6.1 KASAN: use-after-free Read in v4l2_fh_open origin:upstream C 18 1d09h 315d 0/3 upstream: reported C repro on 2024/08/22 03:36

Sample crash report:
==================================================================
BUG: KASAN: slab-use-after-free in v4l2_fh_init drivers/media/v4l2-core/v4l2-fh.c:25 [inline]
BUG: KASAN: slab-use-after-free in v4l2_fh_open+0xca/0x430 drivers/media/v4l2-core/v4l2-fh.c:63
Read of size 8 at addr ffff888055ed0738 by task v4l_id/16080

CPU: 0 PID: 16080 Comm: v4l_id Not tainted 6.6.95-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Call Trace:
 <TASK>
 dump_stack_lvl+0x16c/0x230 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:364 [inline]
 print_report+0xac/0x230 mm/kasan/report.c:475
 kasan_report+0x117/0x150 mm/kasan/report.c:588
 v4l2_fh_init drivers/media/v4l2-core/v4l2-fh.c:25 [inline]
 v4l2_fh_open+0xca/0x430 drivers/media/v4l2-core/v4l2-fh.c:63
 em28xx_v4l2_open+0x157/0x980 drivers/media/usb/em28xx/em28xx-video.c:2153
 v4l2_open+0x212/0x360 drivers/media/v4l2-core/v4l2-dev.c:427
 chrdev_open+0x59e/0x670 fs/char_dev.c:414
 do_dentry_open+0x8c6/0x1500 fs/open.c:929
 do_open fs/namei.c:3632 [inline]
 path_openat+0x274b/0x3190 fs/namei.c:3789
 do_filp_open+0x1c5/0x3d0 fs/namei.c:3816
 do_sys_openat2+0x12c/0x1c0 fs/open.c:1419
 do_sys_open fs/open.c:1434 [inline]
 __do_sys_openat fs/open.c:1450 [inline]
 __se_sys_openat fs/open.c:1445 [inline]
 __x64_sys_openat+0x139/0x160 fs/open.c:1445
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f89ef0a7407
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:00007ffd228f2810 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007f89ef759880 RCX: 00007f89ef0a7407
RDX: 0000000000000000 RSI: 00007ffd228f3f1b RDI: ffffffffffffff9c
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffd228f2a60 R14: 00007f89ef8b8000 R15: 000055e9b20674d8
 </TASK>

Allocated by task 5156:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 ____kasan_kmalloc mm/kasan/common.c:374 [inline]
 __kasan_kmalloc+0x8f/0xa0 mm/kasan/common.c:383
 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:2532
 em28xx_init_extension+0x11c/0x1b0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 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 5156:
 kasan_save_stack mm/kasan/common.c:45 [inline]
 kasan_set_track+0x4e/0x70 mm/kasan/common.c:52
 kasan_save_free_info+0x2e/0x50 mm/kasan/generic.c:522
 ____kasan_slab_free+0x126/0x1e0 mm/kasan/common.c:236
 kasan_slab_free include/linux/kasan.h:164 [inline]
 slab_free_hook mm/slub.c:1806 [inline]
 slab_free_freelist_hook+0x130/0x1b0 mm/slub.c:1832
 slab_free mm/slub.c:3816 [inline]
 __kmem_cache_free+0xba/0x1f0 mm/slub.c:3829
 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:2901
 em28xx_init_extension+0x11c/0x1b0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 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 ffff888055ed0000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 1848 bytes inside of
 freed 8192-byte region [ffff888055ed0000, ffff888055ed2000)

The buggy address belongs to the physical page:
page:ffffea000157b400 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x55ed0
head:ffffea000157b400 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 ffff888017842280 dead000000000122 0000000000000000
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 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 5156, tgid 5156 (kworker/1:3), ts 731522462195, free_ts 731168923243
 set_page_owner include/linux/page_owner.h:31 [inline]
 post_alloc_hook+0x1cd/0x210 mm/page_alloc.c:1554
 prep_new_page mm/page_alloc.c:1561 [inline]
 get_page_from_freelist+0x195c/0x19f0 mm/page_alloc.c:3191
 __alloc_pages+0x1e3/0x460 mm/page_alloc.c:4457
 alloc_slab_page+0x5d/0x170 mm/slub.c:1876
 allocate_slab mm/slub.c:2023 [inline]
 new_slab+0x87/0x2e0 mm/slub.c:2076
 ___slab_alloc+0xc6d/0x12f0 mm/slub.c:3230
 __slab_alloc mm/slub.c:3329 [inline]
 __slab_alloc_node mm/slub.c:3382 [inline]
 slab_alloc_node mm/slub.c:3475 [inline]
 __kmem_cache_alloc_node+0x1a2/0x260 mm/slub.c:3524
 kmalloc_trace+0x2a/0xe0 mm/slab_common.c:1098
 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:2532
 em28xx_init_extension+0x11c/0x1b0 drivers/media/usb/em28xx/em28xx-core.c:1116
 process_one_work kernel/workqueue.c:2634 [inline]
 process_scheduled_works+0xa45/0x15b0 kernel/workqueue.c:2711
 worker_thread+0xa55/0xfc0 kernel/workqueue.c:2792
 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
page last free stack trace:
 reset_page_owner include/linux/page_owner.h:24 [inline]
 free_pages_prepare mm/page_alloc.c:1154 [inline]
 free_unref_page_prepare+0x7ce/0x8e0 mm/page_alloc.c:2336
 free_unref_page+0x32/0x2e0 mm/page_alloc.c:2429
 discard_slab mm/slub.c:2122 [inline]
 __unfreeze_partials+0x1cf/0x210 mm/slub.c:2662
 put_cpu_partial+0x17c/0x250 mm/slub.c:2738
 __slab_free+0x31d/0x410 mm/slub.c:3686
 qlink_free mm/kasan/quarantine.c:166 [inline]
 qlist_free_all+0x75/0xe0 mm/kasan/quarantine.c:185
 kasan_quarantine_reduce+0x143/0x160 mm/kasan/quarantine.c:292
 __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:305
 kasan_slab_alloc include/linux/kasan.h:188 [inline]
 slab_post_alloc_hook+0x6e/0x4d0 mm/slab.h:767
 slab_alloc_node mm/slub.c:3485 [inline]
 slab_alloc mm/slub.c:3493 [inline]
 __kmem_cache_alloc_lru mm/slub.c:3500 [inline]
 kmem_cache_alloc+0x11e/0x2e0 mm/slub.c:3509
 ptlock_alloc mm/memory.c:6155 [inline]
 ptlock_init include/linux/mm.h:2893 [inline]
 pmd_ptlock_init include/linux/mm.h:2993 [inline]
 pagetable_pmd_ctor include/linux/mm.h:3031 [inline]
 pmd_alloc_one include/asm-generic/pgalloc.h:137 [inline]
 __pmd_alloc+0x116/0x880 mm/memory.c:5577
 pmd_alloc include/linux/mm.h:2792 [inline]
 alloc_new_pmd mm/mremap.c:96 [inline]
 move_page_tables+0x1758/0x1910 mm/mremap.c:555
 shift_arg_pages fs/exec.c:713 [inline]
 setup_arg_pages+0xb38/0xed0 fs/exec.c:836
 load_elf_binary+0xb98/0x2700 fs/binfmt_elf.c:1045
 search_binary_handler fs/exec.c:1775 [inline]
 exec_binprm fs/exec.c:1817 [inline]
 bprm_execve+0xaeb/0x16f0 fs/exec.c:1892
 kernel_execve+0x8bd/0x9c0 fs/exec.c:2058

Memory state around the buggy address:
 ffff888055ed0600: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888055ed0680: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888055ed0700: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                        ^
 ffff888055ed0780: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888055ed0800: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (1):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2025/06/29 09:48 linux-6.6.y 3f5b4c104b7d fc9d8ee5 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-6-6-kasan KASAN: slab-use-after-free Read in v4l2_fh_open
* Struck through repros no longer work on HEAD.