syzbot


KASAN: slab-use-after-free Read in em28xx_unregister_media_device

Status: upstream: reported on 2026/01/22 08:53
Subsystems: media
[Documentation on labels]
Reported-by: syzbot+07b93bb3189febcab189@syzkaller.appspotmail.com
First crash: 102d, last: 6d03h
Discussions (3)
Title Replies (including bot) Last reply
[PATCH v2] media: em28xx: fix use-after-free in em28xx_unregister_media_device() 1 (1) 2026/04/21 17:41
[PATCH] media: em28xx: fix use-after-free in em28xx_unregister_media_device() 1 (1) 2026/04/13 14:44
[syzbot] [media?] KASAN: slab-use-after-free Read in em28xx_unregister_media_device 0 (1) 2026/01/22 08:53

Sample crash report:
em28xx 2-1:0.132: Closing input extension
==================================================================
BUG: KASAN: slab-use-after-free in media_device_unregister drivers/media/mc/mc-device.c:833 [inline]
BUG: KASAN: slab-use-after-free in media_device_unregister+0x59d/0x610 drivers/media/mc/mc-device.c:811
Read of size 8 at addr ffff888038974210 by task kworker/1:2/1219

CPU: 1 UID: 0 PID: 1219 Comm: kworker/1:2 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: usb_hub_wq hub_event
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/0x1d0 mm/kasan/report.c:595
 media_device_unregister drivers/media/mc/mc-device.c:833 [inline]
 media_device_unregister+0x59d/0x610 drivers/media/mc/mc-device.c:811
 em28xx_unregister_media_device+0x4e/0xe0 drivers/media/usb/em28xx/em28xx-cards.c:3714
 em28xx_release_resources+0x79/0x1b0 drivers/media/usb/em28xx/em28xx-cards.c:3735
 em28xx_usb_disconnect.cold+0x17d/0x253 drivers/media/usb/em28xx/em28xx-cards.c:4427
 usb_unbind_interface+0x1dd/0x9e0 drivers/usb/core/driver.c:458
 device_remove drivers/base/dd.c:621 [inline]
 device_remove+0x12a/0x180 drivers/base/dd.c:613
 __device_release_driver drivers/base/dd.c:1352 [inline]
 device_release_driver_internal+0x44e/0x620 drivers/base/dd.c:1375
 bus_remove_device+0x2bc/0x560 drivers/base/bus.c:657
 device_del+0x376/0x9b0 drivers/base/core.c:3895
 usb_disable_device+0x367/0x810 drivers/usb/core/message.c:1478
 usb_disconnect+0x2e2/0x9a0 drivers/usb/core/hub.c:2345
 hub_port_connect drivers/usb/core/hub.c:5407 [inline]
 hub_port_connect_change drivers/usb/core/hub.c:5707 [inline]
 port_event drivers/usb/core/hub.c:5871 [inline]
 hub_event+0x1d0c/0x4af0 drivers/usb/core/hub.c:5953
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302
 process_scheduled_works kernel/workqueue.c:3385 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466
 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>

Allocated by task 46:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 poison_kmalloc_redzone mm/kasan/common.c:398 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:415
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 em28xx_v4l2_init.cold+0x94/0x3a40 drivers/media/usb/em28xx/em28xx-video.c:2707
 em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1248
 request_module_async+0x61/0x80 drivers/media/usb/em28xx/em28xx-cards.c:3660
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302
 process_scheduled_works kernel/workqueue.c:3385 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466
 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

Freed by task 46:
 kasan_save_stack+0x30/0x50 mm/kasan/common.c:57
 kasan_save_track+0x14/0x30 mm/kasan/common.c:78
 kasan_save_free_info+0x3b/0x70 mm/kasan/generic.c:584
 poison_slab_object mm/kasan/common.c:253 [inline]
 __kasan_slab_free+0x5f/0x80 mm/kasan/common.c:285
 kasan_slab_free include/linux/kasan.h:235 [inline]
 slab_free_hook mm/slub.c:2689 [inline]
 slab_free mm/slub.c:6246 [inline]
 kfree+0x223/0x6c0 mm/slub.c:6561
 kref_put.isra.0+0x53/0x75 include/linux/kref.h:65
 em28xx_v4l2_init.cold+0x280/0x3a40 drivers/media/usb/em28xx/em28xx-video.c:3078
 em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1248
 request_module_async+0x61/0x80 drivers/media/usb/em28xx/em28xx-cards.c:3660
 process_one_work+0xa0e/0x1980 kernel/workqueue.c:3302
 process_scheduled_works kernel/workqueue.c:3385 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3466
 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

The buggy address belongs to the object at ffff888038974000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 528 bytes inside of
 freed 8192-byte region [ffff888038974000, ffff888038976000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x38970
head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000040(head|node=0|zone=1|lastcpupid=0x7ff)
page_type: f5(slab)
raw: 00fff00000000040 ffff88813fe8d280 dead000000000100 dead000000000122
raw: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813fe8d280 dead000000000100 dead000000000122
head: 0000000000000000 0000000800020002 00000000f5000000 0000000000000000
head: 00fff00000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff
head: ffffffffffffffff 0000000000000000 00000000ffffffff 0000000000000008
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 5469, tgid 5469 (S30dbus), ts 44234534534, free_ts 44150828622
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x153/0x170 mm/page_alloc.c:1858
 prep_new_page mm/page_alloc.c:1866 [inline]
 get_page_from_freelist+0x11a6/0x33b0 mm/page_alloc.c:3946
 __alloc_frozen_pages_noprof+0x27c/0x2bc0 mm/page_alloc.c:5226
 alloc_slab_page mm/slub.c:3278 [inline]
 allocate_slab mm/slub.c:3467 [inline]
 new_slab+0xa6/0x6c0 mm/slub.c:3525
 refill_objects+0x277/0x420 mm/slub.c:7251
 refill_sheaf mm/slub.c:2816 [inline]
 __pcs_replace_empty_main+0x375/0x650 mm/slub.c:4651
 alloc_from_pcs mm/slub.c:4749 [inline]
 slab_alloc_node mm/slub.c:4883 [inline]
 __kmalloc_cache_noprof+0x493/0x6f0 mm/slub.c:5410
 kmalloc_noprof include/linux/slab.h:950 [inline]
 kzalloc_noprof include/linux/slab.h:1188 [inline]
 tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
 tomoyo_init_log+0xc4f/0x20c0 security/tomoyo/audit.c:262
 tomoyo_supervisor+0x506/0x1340 security/tomoyo/common.c:2232
 tomoyo_audit_env_log security/tomoyo/environ.c:37 [inline]
 tomoyo_env_perm+0x191/0x200 security/tomoyo/environ.c:64
 tomoyo_environ security/tomoyo/domain.c:673 [inline]
 tomoyo_find_next_domain+0x13d7/0x2010 security/tomoyo/domain.c:889
 tomoyo_bprm_check_security security/tomoyo/tomoyo.c:102 [inline]
 tomoyo_bprm_check_security+0x12d/0x1d0 security/tomoyo/tomoyo.c:92
 security_bprm_check+0x87/0x1e0 security/security.c:820
 search_binary_handler fs/exec.c:1654 [inline]
 exec_binprm fs/exec.c:1696 [inline]
 bprm_execve fs/exec.c:1748 [inline]
 bprm_execve+0x845/0x1650 fs/exec.c:1724
 do_execveat_common.isra.0+0x4a5/0x580 fs/exec.c:1846
 __do_sys_execve fs/exec.c:1930 [inline]
 __se_sys_execve fs/exec.c:1924 [inline]
 __x64_sys_execve+0x93/0xd0 fs/exec.c:1924
page last free pid 5194 tgid 5194 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 __free_pages_prepare mm/page_alloc.c:1402 [inline]
 __free_frozen_pages+0x747/0x1040 mm/page_alloc.c:2943
 qlink_free mm/kasan/quarantine.c:163 [inline]
 qlist_free_all+0x47/0xf0 mm/kasan/quarantine.c:179
 kasan_quarantine_reduce+0x1a0/0x1f0 mm/kasan/quarantine.c:286
 __kasan_slab_alloc+0x69/0x90 mm/kasan/common.c:350
 kasan_slab_alloc include/linux/kasan.h:253 [inline]
 slab_post_alloc_hook mm/slub.c:4569 [inline]
 slab_alloc_node mm/slub.c:4898 [inline]
 kmem_cache_alloc_noprof+0x241/0x6e0 mm/slub.c:4905
 lsm_file_alloc security/security.c:171 [inline]
 security_file_alloc+0x34/0x2c0 security/security.c:2406
 init_file+0x95/0x480 fs/file_table.c:184
 alloc_empty_file+0x79/0x1c0 fs/file_table.c:266
 path_openat+0xe8/0x31a0 fs/namei.c:4844
 do_file_open+0x20e/0x430 fs/namei.c:4887
 do_sys_openat2+0x10d/0x1e0 fs/open.c:1364
 do_sys_open fs/open.c:1370 [inline]
 __do_sys_openat fs/open.c:1386 [inline]
 __se_sys_openat fs/open.c:1381 [inline]
 __x64_sys_openat+0x12d/0x210 fs/open.c:1381
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x10b/0xf80 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888038974100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888038974180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888038974200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                         ^
 ffff888038974280: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888038974300: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================

Crashes (14):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/04/24 20:14 upstream dd6c438c3e64 1c2b9291 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/04/22 02:03 upstream 4ee64205ffaa 0b6ab7ec .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/04/19 11:34 upstream faeab166167f 303e2802 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/04/08 09:59 upstream 3036cd0d3328 2c961e87 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/04/03 06:22 upstream d8a9a4b11a13 4440e7c2 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/03/29 18:18 upstream cbfffcca2bf0 356bdfc9 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/02/20 21:46 upstream 8bf22c33e7a1 741f5161 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/02/20 21:39 upstream 8bf22c33e7a1 741f5161 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/02/10 11:03 upstream 8a5203c630c6 4ab09a02 .config console log report info [disk image] [vmlinux] [kernel image] ci-upstream-kasan-gce-selinux-root KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/04/15 04:29 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing 87117347a0e7 e2e976a8 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/03/22 15:29 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing 84db3719d273 5b92003d .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/01/30 17:01 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing 0a06917432a7 ae7dc18c .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/01/21 07:33 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing 5ac87cd859ec 6f1aa2f9 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb KASAN: slab-use-after-free Read in em28xx_unregister_media_device
2026/01/18 05:05 https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git usb-testing fa3bb5011f33 20d37d28 .config console log report info [disk image] [vmlinux] [kernel image] ci2-upstream-usb KASAN: slab-use-after-free Read in em28xx_unregister_media_device
* Struck through repros no longer work on HEAD.