* [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put
@ 2026-10-22 0:29 syzbot
2026-10-22 12:11 ` Forwarded: media: em28xx: fix refcount underflow caused by em28xx_free_v4l2 syzbot
` (3 more replies)
0 siblings, 4 replies; 5+ messages in thread
From: syzbot @ 2026-10-22 0:29 UTC (permalink / raw)
To: linux-kernel, linux-media, linux-usb, mchehab, syzkaller-bugs
Hello,
syzbot found the following issue on:
HEAD commit: 8f7df005a756 Add linux-next specific files for 20261020
git tree: linux-next
console+strace: https://syzkaller.appspot.com/x/log.txt?x=1061bb05580000
kernel config: https://syzkaller.appspot.com/x/.config?x=9c1b9b13e3e4ce1a
dashboard link: https://syzkaller.appspot.com/bug?extid=809dfc586f33fc44b6ac
compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=1104258e580000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=176a5481580000
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/4ecf38da9706/disk-8f7df005.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/feab027e2efe/vmlinux-8f7df005.xz
kernel image: https://storage.googleapis.com/syzbot-assets/ded91a573e5a/bzImage-8f7df005.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+809dfc586f33fc44b6ac@syzkaller.appspotmail.com
refcount_t: underflow; use-after-free.
------------[ cut here ]------------
kernel BUG at lib/refcount.c:37!
Oops: invalid opcode: 0000 [#1] SMP KASAN PTI
CPU: 1 UID: 0 PID: 7562 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
RIP: 0010:refcount_warn_saturate+0x104/0x110 lib/refcount.c:37
Code: 5d ff ff ff e8 4d c1 d1 fc 48 c7 c7 00 e3 8d 8c e8 61 69 30 fc 90 0f 0b e8 39 c1 d1 fc 48 c7 c7 80 e3 8d 8c e8 4d 69 30 fc 90 <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900065b7cc0 EFLAGS: 00010246
RAX: 0000000000000026 RBX: 0000000000000003 RCX: 86d7792bd9d84300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff90033f40
RBP: 0000000000000000 R08: ffffffff81a6b7f0 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff237c1d8 R12: 1ffffffff1973318
R13: dffffc0000000000 R14: ffff88807cc000b0 R15: ffffffff882fcb70
FS: 00007f2b1fb76880(0000) GS:ffff8881234da000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055aef7b1964d CR3: 0000000075e40000 CR4: 00000000003526f0
Call Trace:
<TASK>
__refcount_sub_and_test include/linux/refcount.h:400 [inline]
__refcount_dec_and_test include/linux/refcount.h:432 [inline]
refcount_dec_and_test include/linux/refcount.h:450 [inline]
kref_put include/linux/kref.h:64 [inline]
v4l2_device_put+0xc2/0xd0 drivers/media/v4l2-core/v4l2-device.c:56
device_release+0xc4/0x1f0 drivers/base/core.c:-1
kobject_cleanup lib/kobject.c:689 [inline]
kobject_release lib/kobject.c:720 [inline]
kref_put include/linux/kref.h:65 [inline]
kobject_put+0x222/0x550 lib/kobject.c:737
video_put drivers/media/v4l2-core/v4l2-dev.c:173 [inline]
v4l2_release+0x273/0x350 drivers/media/v4l2-core/v4l2-dev.c:480
__fput+0x408/0xa40 fs/file_table.c:513
fput_close_sync+0x11f/0x240 fs/file_table.c:619
filp_close_sync fs/open.c:1897 [inline]
__do_sys_close fs/open.c:2153 [inline]
__se_sys_close+0xa2/0x160 fs/open.c:2140
do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f2b1f4a7407
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:00007fffdbbfc440 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007f2b1fb76880 RCX: 00007f2b1f4a7407
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007f2b1fb766e8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000013
R13: 00007fffdbbfc670 R14: 00007f2b1fcdd000 R15: 000055aef7b1d4d8
</TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
RIP: 0010:refcount_warn_saturate+0x104/0x110 lib/refcount.c:37
Code: 5d ff ff ff e8 4d c1 d1 fc 48 c7 c7 00 e3 8d 8c e8 61 69 30 fc 90 0f 0b e8 39 c1 d1 fc 48 c7 c7 80 e3 8d 8c e8 4d 69 30 fc 90 <0f> 0b 66 2e 0f 1f 84 00 00 00 00 00 90 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffc900065b7cc0 EFLAGS: 00010246
RAX: 0000000000000026 RBX: 0000000000000003 RCX: 86d7792bd9d84300
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff90033f40
RBP: 0000000000000000 R08: ffffffff81a6b7f0 R09: 0000000000000000
R10: dffffc0000000000 R11: fffffbfff237c1d8 R12: 1ffffffff1973318
R13: dffffc0000000000 R14: ffff88807cc000b0 R15: ffffffff882fcb70
FS: 00007f2b1fb76880(0000) GS:ffff8881234da000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000055aef7b1964d CR3: 0000000075e40000 CR4: 00000000003526f0
---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
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syzbot will keep track of this issue. See:
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If the report is already addressed, let syzbot know by replying with:
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If you want syzbot to run the reproducer, reply with:
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^ permalink raw reply [flat|nested] 5+ messages in thread* Forwarded: media: em28xx: fix refcount underflow caused by em28xx_free_v4l2
2026-10-22 0:29 [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put syzbot
@ 2026-10-22 12:11 ` syzbot
2026-10-22 14:53 ` Forwarded: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put syzbot
` (2 subsequent siblings)
3 siblings, 0 replies; 5+ messages in thread
From: syzbot @ 2026-10-22 12:11 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: media: em28xx: fix refcount underflow caused by em28xx_free_v4l2
Author: neganhat@gmail.com
#syz test: linux-next 8f7df005a756
^ permalink raw reply [flat|nested] 5+ messages in thread* Forwarded: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put
2026-10-22 0:29 [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put syzbot
2026-10-22 12:11 ` Forwarded: media: em28xx: fix refcount underflow caused by em28xx_free_v4l2 syzbot
@ 2026-10-22 14:53 ` syzbot
2026-10-22 16:17 ` syzbot
2026-11-01 20:39 ` Forwarded: [PATCH] media: em28xx: fix v4l2 use-after-free after failed init syzbot
3 siblings, 0 replies; 5+ messages in thread
From: syzbot @ 2026-10-22 14:53 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put
Author: neganhat@gmail.com
#syz test: linux-next 8f7df005a756
On Thu, Oct 22, 2026 at 9:08 PM syzbot
<syzbot+809dfc586f33fc44b6ac@syzkaller.appspotmail.com> wrote:
>
> Hello,
>
> syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> KASAN: slab-use-after-free Read in v4l2_release
>
> ==================================================================
> BUG: KASAN: slab-use-after-free in v4l2_device_supports_requests include/media/v4l2-device.h:252 [inline]
> BUG: KASAN: slab-use-after-free in v4l2_release+0xfe/0x350 drivers/media/v4l2-core/v4l2-dev.c:466
> Read of size 8 at addr ffff888035785b10 by task v4l_id/7282
>
> CPU: 1 UID: 0 PID: 7282 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full)
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
> Call Trace:
> <TASK>
> dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
> print_address_description+0x55/0x1e0 mm/kasan/report.c:378
> print_report+0x58/0x70 mm/kasan/report.c:482
> kasan_report+0x117/0x150 mm/kasan/report.c:595
> v4l2_device_supports_requests include/media/v4l2-device.h:252 [inline]
> v4l2_release+0xfe/0x350 drivers/media/v4l2-core/v4l2-dev.c:466
> __fput+0x408/0xa40 fs/file_table.c:513
> fput_close_sync+0x11f/0x240 fs/file_table.c:619
> filp_close_sync fs/open.c:1897 [inline]
> __do_sys_close fs/open.c:2153 [inline]
> __se_sys_close+0xa2/0x160 fs/open.c:2140
> do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
> entry_SYSCALL_64_after_hwframe+0x77/0x7f
> RIP: 0033:0x7f4a56ca7407
> 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:00007ffcfee18b00 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
> RAX: ffffffffffffffda RBX: 00007f4a57357880 RCX: 00007f4a56ca7407
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
> RBP: 00007f4a573576e8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000013
> R13: 00007ffcfee18d30 R14: 00007f4a5745c000 R15: 0000557c8543f4d8
> </TASK>
>
> Allocated by task 5749:
> kasan_save_stack mm/kasan/common.c:57 [inline]
> kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> poison_kmalloc_redzone mm/kasan/common.c:409 [inline]
> __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426
> kasan_kmalloc include/linux/kasan.h:263 [inline]
> __kmalloc_cache_noprof+0x31c/0x600 mm/slub.c:5680
> _kmalloc_noprof include/linux/slab.h:991 [inline]
> _kzalloc_noprof include/linux/slab.h:1312 [inline]
> em28xx_media_device_init drivers/media/usb/em28xx/em28xx-cards.c:3757 [inline]
> em28xx_init_dev+0x857/0x2680 drivers/media/usb/em28xx/em28xx-cards.c:3947
> em28xx_usb_probe+0x17b2/0x2dd0 drivers/media/usb/em28xx/em28xx-cards.c:4324
> usb_probe_interface+0x751/0xe00 drivers/usb/core/driver.c:399
> call_driver_probe drivers/base/dd.c:-1 [inline]
> really_probe+0x254/0xae0 drivers/base/dd.c:707
> __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:869
> driver_probe_device+0x4f/0x240 drivers/base/dd.c:899
> __device_attach_driver+0x270/0x410 drivers/base/dd.c:1027
> bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:503
> __device_attach+0x2bd/0x430 drivers/base/dd.c:1131
> device_initial_probe+0x9c/0x100 drivers/base/dd.c:1190
> __bus_probe_device+0x126/0x220 drivers/base/bus.c:617
> device_add+0x7d7/0xb80 drivers/base/core.c:3776
> usb_set_configuration+0x1bb5/0x2260 drivers/usb/core/message.c:2280
> usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
> usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:293
> call_driver_probe drivers/base/dd.c:-1 [inline]
> really_probe+0x254/0xae0 drivers/base/dd.c:707
> __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:869
> driver_probe_device+0x4f/0x240 drivers/base/dd.c:899
> __device_attach_driver+0x270/0x410 drivers/base/dd.c:1027
> bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:503
> __device_attach+0x2bd/0x430 drivers/base/dd.c:1131
> device_initial_probe+0x9c/0x100 drivers/base/dd.c:1190
> __bus_probe_device+0x126/0x220 drivers/base/bus.c:617
> device_add+0x7d7/0xb80 drivers/base/core.c:3776
> usb_new_device+0x9aa/0x1690 drivers/usb/core/hub.c:2713
> hub_port_connect drivers/usb/core/hub.c:5585 [inline]
> hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
> port_event drivers/usb/core/hub.c:5889 [inline]
> hub_event+0x28e8/0x4d30 drivers/usb/core/hub.c:5971
> process_one_work kernel/workqueue.c:3495 [inline]
> process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
> worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
> kthread+0x38b/0x480 kernel/kthread.c:436
> ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
>
> Freed by task 5749:
> kasan_save_stack mm/kasan/common.c:57 [inline]
> kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
> poison_slab_object mm/kasan/common.c:264 [inline]
> __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296
> kasan_slab_free include/linux/kasan.h:235 [inline]
> slab_free_hook mm/slub.c:2780 [inline]
> slab_free mm/slub.c:6630 [inline]
> kfree+0x1c5/0x650 mm/slub.c:6923
> em28xx_unregister_media_device drivers/media/usb/em28xx/em28xx-cards.c:3779 [inline]
> em28xx_release_resources+0xde/0x240 drivers/media/usb/em28xx/em28xx-cards.c:3798
> em28xx_usb_disconnect+0x19f/0x2f0 drivers/media/usb/em28xx/em28xx-cards.c:4493
> usb_unbind_interface+0x295/0x9c0 drivers/usb/core/driver.c:460
> device_remove drivers/base/dd.c:619 [inline]
> __device_release_driver drivers/base/dd.c:1357 [inline]
> device_release_driver_internal+0x48d/0x7d0 drivers/base/dd.c:1380
> bus_remove_device+0x444/0x560 drivers/base/bus.c:681
> device_del+0x524/0x8f0 drivers/base/core.c:3965
> usb_disable_device+0x3d4/0x8d0 drivers/usb/core/message.c:1484
> usb_disconnect+0x346/0x9a0 drivers/usb/core/hub.c:2355
> hub_port_connect drivers/usb/core/hub.c:5425 [inline]
> hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
> port_event drivers/usb/core/hub.c:5889 [inline]
> hub_event+0x1bbb/0x4d30 drivers/usb/core/hub.c:5971
> process_one_work kernel/workqueue.c:3495 [inline]
> process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
> worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
> kthread+0x38b/0x480 kernel/kthread.c:436
> ret_from_fork+0x514/0xb70 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 ffff888035785800
> which belongs to the cache kmalloc-1k of size 1024
> The buggy address is located 784 bytes inside of
> freed 1024-byte region [ffff888035785800, ffff888035785c00)
>
> The buggy address belongs to the physical page:
> page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x35780
> 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 ffff88813ff2bdc0 dead000000000100 dead000000000122
> raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
> head: 00fff00000000040 ffff88813ff2bdc0 dead000000000100 dead000000000122
> head: 0000000000000000 0000000000100010 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 162, tgid 162 (kworker/u8:7), ts 176383093465
> set_page_owner include/linux/page_owner.h:33 [inline]
> post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1856
> prep_new_page mm/page_alloc.c:1864 [inline]
> get_page_from_freelist+0x220f/0x2280 mm/page_alloc.c:3935
> __alloc_frozen_pages_noprof+0x1fe/0x410 mm/page_alloc.c:5459
> alloc_slab_page mm/slub.c:3384 [inline]
> allocate_slab+0x7d/0x5e0 mm/slub.c:3499
> new_slab mm/slub.c:3550 [inline]
> refill_objects+0x2d5/0x350 mm/slub.c:7539
> refill_sheaf mm/slub.c:2917 [inline]
> __pcs_replace_empty_main+0x2c8/0x6c0 mm/slub.c:4811
> alloc_from_pcs mm/slub.c:4887 [inline]
> slab_alloc_node mm/slub.c:5021 [inline]
> __do_kmalloc_node mm/slub.c:5530 [inline]
> __kmalloc_noprof+0x476/0x710 mm/slub.c:5556
> _kmalloc_noprof include/linux/slab.h:995 [inline]
> _kzalloc_noprof include/linux/slab.h:1312 [inline]
> ieee802_11_parse_elems_full+0x14b/0x2a10 net/mac80211/parse.c:1077
> ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2583 [inline]
> ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1542 [inline]
> ieee80211_ibss_rx_queued_mgmt+0x509/0x2c40 net/mac80211/ibss.c:1573
> ieee80211_iface_process_skb net/mac80211/iface.c:1805 [inline]
> ieee80211_iface_work+0x769/0xfa0 net/mac80211/iface.c:1859
> cfg80211_wiphy_work+0x29e/0x420 net/wireless/core.c:610
> process_one_work kernel/workqueue.c:3495 [inline]
> process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
> worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
> kthread+0x38b/0x480 kernel/kthread.c:436
> ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> page last free pid 31 tgid 31 ts 176051931514 stack trace:
> reset_page_owner include/linux/page_owner.h:26 [inline]
> __free_pages_prepare mm/page_alloc.c:1403 [inline]
> __free_frozen_pages+0xc97/0xd90 mm/page_alloc.c:2954
> __slab_free+0x269/0x2c0 mm/slub.c:5926
> qlink_free mm/kasan/quarantine.c:163 [inline]
> qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
> kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
> __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:361
> kasan_slab_alloc include/linux/kasan.h:253 [inline]
> slab_post_alloc_hook mm/slub.c:4720 [inline]
> slab_alloc_node mm/slub.c:5033 [inline]
> __kmalloc_cache_noprof+0x29a/0x600 mm/slub.c:5676
> _kmalloc_noprof include/linux/slab.h:991 [inline]
> dummy_urb_enqueue+0x7c/0x7a0 drivers/usb/gadget/udc/dummy_hcd.c:1327
> usb_hcd_submit_urb+0x328/0x1b60 drivers/usb/core/hcd.c:1543
> usb_start_wait_urb+0x13f/0x5b0 drivers/usb/core/message.c:62
> usb_internal_control_msg drivers/usb/core/message.c:117 [inline]
> usb_control_msg+0x234/0x3e0 drivers/usb/core/message.c:167
> get_bMaxPacketSize0 drivers/usb/core/hub.c:4869 [inline]
> hub_port_init+0xb0b/0x28c0 drivers/usb/core/hub.c:5065
> hub_port_connect drivers/usb/core/hub.c:5514 [inline]
> hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
> port_event drivers/usb/core/hub.c:5889 [inline]
> hub_event+0x24e8/0x4d30 drivers/usb/core/hub.c:5971
> process_one_work kernel/workqueue.c:3495 [inline]
> process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
> worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
> kthread+0x38b/0x480 kernel/kthread.c:436
> ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
>
> Memory state around the buggy address:
> ffff888035785a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888035785a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> >ffff888035785b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ^
> ffff888035785b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> ffff888035785c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> ==================================================================
>
>
> Tested on:
>
> commit: 8f7df005 Add linux-next specific files for 20261020
> git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> console output: https://syzkaller.appspot.com/x/log.txt?x=120a9fa9580000
> kernel config: https://syzkaller.appspot.com/x/.config?x=9c1b9b13e3e4ce1a
> dashboard link: https://syzkaller.appspot.com/bug?extid=809dfc586f33fc44b6ac
> compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
> patch: https://syzkaller.appspot.com/x/patch.diff?x=17b7b50d580000
>
^ permalink raw reply [flat|nested] 5+ messages in thread
* Forwarded: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put
2026-10-22 0:29 [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put syzbot
2026-10-22 12:11 ` Forwarded: media: em28xx: fix refcount underflow caused by em28xx_free_v4l2 syzbot
2026-10-22 14:53 ` Forwarded: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put syzbot
@ 2026-10-22 16:17 ` syzbot
2026-11-01 20:39 ` Forwarded: [PATCH] media: em28xx: fix v4l2 use-after-free after failed init syzbot
3 siblings, 0 replies; 5+ messages in thread
From: syzbot @ 2026-10-22 16:17 UTC (permalink / raw)
To: linux-kernel, syzkaller-bugs
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org, syzkaller-bugs@googlegroups.com.
***
Subject: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put
Author: neganhat@gmail.com
#syz test: linux-next 8f7df005a756
On Thu, Oct 22, 2026 at 9:52 PM Nhật Anh Nguyễn Duy <neganhat@gmail.com> wrote:
>
> #syz test: linux-next 8f7df005a756
>
> On Thu, Oct 22, 2026 at 9:08 PM syzbot
> <syzbot+809dfc586f33fc44b6ac@syzkaller.appspotmail.com> wrote:
> >
> > Hello,
> >
> > syzbot has tested the proposed patch but the reproducer is still triggering an issue:
> > KASAN: slab-use-after-free Read in v4l2_release
> >
> > ==================================================================
> > BUG: KASAN: slab-use-after-free in v4l2_device_supports_requests include/media/v4l2-device.h:252 [inline]
> > BUG: KASAN: slab-use-after-free in v4l2_release+0xfe/0x350 drivers/media/v4l2-core/v4l2-dev.c:466
> > Read of size 8 at addr ffff888035785b10 by task v4l_id/7282
> >
> > CPU: 1 UID: 0 PID: 7282 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full)
> > Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/07/2026
> > Call Trace:
> > <TASK>
> > dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
> > print_address_description+0x55/0x1e0 mm/kasan/report.c:378
> > print_report+0x58/0x70 mm/kasan/report.c:482
> > kasan_report+0x117/0x150 mm/kasan/report.c:595
> > v4l2_device_supports_requests include/media/v4l2-device.h:252 [inline]
> > v4l2_release+0xfe/0x350 drivers/media/v4l2-core/v4l2-dev.c:466
> > __fput+0x408/0xa40 fs/file_table.c:513
> > fput_close_sync+0x11f/0x240 fs/file_table.c:619
> > filp_close_sync fs/open.c:1897 [inline]
> > __do_sys_close fs/open.c:2153 [inline]
> > __se_sys_close+0xa2/0x160 fs/open.c:2140
> > do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
> > do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
> > entry_SYSCALL_64_after_hwframe+0x77/0x7f
> > RIP: 0033:0x7f4a56ca7407
> > 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:00007ffcfee18b00 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
> > RAX: ffffffffffffffda RBX: 00007f4a57357880 RCX: 00007f4a56ca7407
> > RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
> > RBP: 00007f4a573576e8 R08: 0000000000000000 R09: 0000000000000000
> > R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000013
> > R13: 00007ffcfee18d30 R14: 00007f4a5745c000 R15: 0000557c8543f4d8
> > </TASK>
> >
> > Allocated by task 5749:
> > kasan_save_stack mm/kasan/common.c:57 [inline]
> > kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> > poison_kmalloc_redzone mm/kasan/common.c:409 [inline]
> > __kasan_kmalloc+0x93/0xb0 mm/kasan/common.c:426
> > kasan_kmalloc include/linux/kasan.h:263 [inline]
> > __kmalloc_cache_noprof+0x31c/0x600 mm/slub.c:5680
> > _kmalloc_noprof include/linux/slab.h:991 [inline]
> > _kzalloc_noprof include/linux/slab.h:1312 [inline]
> > em28xx_media_device_init drivers/media/usb/em28xx/em28xx-cards.c:3757 [inline]
> > em28xx_init_dev+0x857/0x2680 drivers/media/usb/em28xx/em28xx-cards.c:3947
> > em28xx_usb_probe+0x17b2/0x2dd0 drivers/media/usb/em28xx/em28xx-cards.c:4324
> > usb_probe_interface+0x751/0xe00 drivers/usb/core/driver.c:399
> > call_driver_probe drivers/base/dd.c:-1 [inline]
> > really_probe+0x254/0xae0 drivers/base/dd.c:707
> > __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:869
> > driver_probe_device+0x4f/0x240 drivers/base/dd.c:899
> > __device_attach_driver+0x270/0x410 drivers/base/dd.c:1027
> > bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:503
> > __device_attach+0x2bd/0x430 drivers/base/dd.c:1131
> > device_initial_probe+0x9c/0x100 drivers/base/dd.c:1190
> > __bus_probe_device+0x126/0x220 drivers/base/bus.c:617
> > device_add+0x7d7/0xb80 drivers/base/core.c:3776
> > usb_set_configuration+0x1bb5/0x2260 drivers/usb/core/message.c:2280
> > usb_generic_driver_probe+0x8d/0x150 drivers/usb/core/generic.c:250
> > usb_probe_device+0x1c3/0x3b0 drivers/usb/core/driver.c:293
> > call_driver_probe drivers/base/dd.c:-1 [inline]
> > really_probe+0x254/0xae0 drivers/base/dd.c:707
> > __driver_probe_device+0x1e8/0x360 drivers/base/dd.c:869
> > driver_probe_device+0x4f/0x240 drivers/base/dd.c:899
> > __device_attach_driver+0x270/0x410 drivers/base/dd.c:1027
> > bus_for_each_drv+0x258/0x2f0 drivers/base/bus.c:503
> > __device_attach+0x2bd/0x430 drivers/base/dd.c:1131
> > device_initial_probe+0x9c/0x100 drivers/base/dd.c:1190
> > __bus_probe_device+0x126/0x220 drivers/base/bus.c:617
> > device_add+0x7d7/0xb80 drivers/base/core.c:3776
> > usb_new_device+0x9aa/0x1690 drivers/usb/core/hub.c:2713
> > hub_port_connect drivers/usb/core/hub.c:5585 [inline]
> > hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
> > port_event drivers/usb/core/hub.c:5889 [inline]
> > hub_event+0x28e8/0x4d30 drivers/usb/core/hub.c:5971
> > process_one_work kernel/workqueue.c:3495 [inline]
> > process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
> > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
> > kthread+0x38b/0x480 kernel/kthread.c:436
> > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> >
> > Freed by task 5749:
> > kasan_save_stack mm/kasan/common.c:57 [inline]
> > kasan_save_track+0x3e/0x80 mm/kasan/common.c:78
> > kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:584
> > poison_slab_object mm/kasan/common.c:264 [inline]
> > __kasan_slab_free+0x5c/0x80 mm/kasan/common.c:296
> > kasan_slab_free include/linux/kasan.h:235 [inline]
> > slab_free_hook mm/slub.c:2780 [inline]
> > slab_free mm/slub.c:6630 [inline]
> > kfree+0x1c5/0x650 mm/slub.c:6923
> > em28xx_unregister_media_device drivers/media/usb/em28xx/em28xx-cards.c:3779 [inline]
> > em28xx_release_resources+0xde/0x240 drivers/media/usb/em28xx/em28xx-cards.c:3798
> > em28xx_usb_disconnect+0x19f/0x2f0 drivers/media/usb/em28xx/em28xx-cards.c:4493
> > usb_unbind_interface+0x295/0x9c0 drivers/usb/core/driver.c:460
> > device_remove drivers/base/dd.c:619 [inline]
> > __device_release_driver drivers/base/dd.c:1357 [inline]
> > device_release_driver_internal+0x48d/0x7d0 drivers/base/dd.c:1380
> > bus_remove_device+0x444/0x560 drivers/base/bus.c:681
> > device_del+0x524/0x8f0 drivers/base/core.c:3965
> > usb_disable_device+0x3d4/0x8d0 drivers/usb/core/message.c:1484
> > usb_disconnect+0x346/0x9a0 drivers/usb/core/hub.c:2355
> > hub_port_connect drivers/usb/core/hub.c:5425 [inline]
> > hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
> > port_event drivers/usb/core/hub.c:5889 [inline]
> > hub_event+0x1bbb/0x4d30 drivers/usb/core/hub.c:5971
> > process_one_work kernel/workqueue.c:3495 [inline]
> > process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
> > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
> > kthread+0x38b/0x480 kernel/kthread.c:436
> > ret_from_fork+0x514/0xb70 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 ffff888035785800
> > which belongs to the cache kmalloc-1k of size 1024
> > The buggy address is located 784 bytes inside of
> > freed 1024-byte region [ffff888035785800, ffff888035785c00)
> >
> > The buggy address belongs to the physical page:
> > page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x35780
> > 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 ffff88813ff2bdc0 dead000000000100 dead000000000122
> > raw: 0000000000000000 0000000000100010 00000000f5000000 0000000000000000
> > head: 00fff00000000040 ffff88813ff2bdc0 dead000000000100 dead000000000122
> > head: 0000000000000000 0000000000100010 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 0xd2820(GFP_ATOMIC|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 162, tgid 162 (kworker/u8:7), ts 176383093465
> > set_page_owner include/linux/page_owner.h:33 [inline]
> > post_alloc_hook+0x1f9/0x250 mm/page_alloc.c:1856
> > prep_new_page mm/page_alloc.c:1864 [inline]
> > get_page_from_freelist+0x220f/0x2280 mm/page_alloc.c:3935
> > __alloc_frozen_pages_noprof+0x1fe/0x410 mm/page_alloc.c:5459
> > alloc_slab_page mm/slub.c:3384 [inline]
> > allocate_slab+0x7d/0x5e0 mm/slub.c:3499
> > new_slab mm/slub.c:3550 [inline]
> > refill_objects+0x2d5/0x350 mm/slub.c:7539
> > refill_sheaf mm/slub.c:2917 [inline]
> > __pcs_replace_empty_main+0x2c8/0x6c0 mm/slub.c:4811
> > alloc_from_pcs mm/slub.c:4887 [inline]
> > slab_alloc_node mm/slub.c:5021 [inline]
> > __do_kmalloc_node mm/slub.c:5530 [inline]
> > __kmalloc_noprof+0x476/0x710 mm/slub.c:5556
> > _kmalloc_noprof include/linux/slab.h:995 [inline]
> > _kzalloc_noprof include/linux/slab.h:1312 [inline]
> > ieee802_11_parse_elems_full+0x14b/0x2a10 net/mac80211/parse.c:1077
> > ieee802_11_parse_elems net/mac80211/ieee80211_i.h:2583 [inline]
> > ieee80211_rx_mgmt_probe_beacon net/mac80211/ibss.c:1542 [inline]
> > ieee80211_ibss_rx_queued_mgmt+0x509/0x2c40 net/mac80211/ibss.c:1573
> > ieee80211_iface_process_skb net/mac80211/iface.c:1805 [inline]
> > ieee80211_iface_work+0x769/0xfa0 net/mac80211/iface.c:1859
> > cfg80211_wiphy_work+0x29e/0x420 net/wireless/core.c:610
> > process_one_work kernel/workqueue.c:3495 [inline]
> > process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
> > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
> > kthread+0x38b/0x480 kernel/kthread.c:436
> > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> > ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
> > page last free pid 31 tgid 31 ts 176051931514 stack trace:
> > reset_page_owner include/linux/page_owner.h:26 [inline]
> > __free_pages_prepare mm/page_alloc.c:1403 [inline]
> > __free_frozen_pages+0xc97/0xd90 mm/page_alloc.c:2954
> > __slab_free+0x269/0x2c0 mm/slub.c:5926
> > qlink_free mm/kasan/quarantine.c:163 [inline]
> > qlist_free_all+0x99/0x100 mm/kasan/quarantine.c:179
> > kasan_quarantine_reduce+0x148/0x160 mm/kasan/quarantine.c:286
> > __kasan_slab_alloc+0x22/0x80 mm/kasan/common.c:361
> > kasan_slab_alloc include/linux/kasan.h:253 [inline]
> > slab_post_alloc_hook mm/slub.c:4720 [inline]
> > slab_alloc_node mm/slub.c:5033 [inline]
> > __kmalloc_cache_noprof+0x29a/0x600 mm/slub.c:5676
> > _kmalloc_noprof include/linux/slab.h:991 [inline]
> > dummy_urb_enqueue+0x7c/0x7a0 drivers/usb/gadget/udc/dummy_hcd.c:1327
> > usb_hcd_submit_urb+0x328/0x1b60 drivers/usb/core/hcd.c:1543
> > usb_start_wait_urb+0x13f/0x5b0 drivers/usb/core/message.c:62
> > usb_internal_control_msg drivers/usb/core/message.c:117 [inline]
> > usb_control_msg+0x234/0x3e0 drivers/usb/core/message.c:167
> > get_bMaxPacketSize0 drivers/usb/core/hub.c:4869 [inline]
> > hub_port_init+0xb0b/0x28c0 drivers/usb/core/hub.c:5065
> > hub_port_connect drivers/usb/core/hub.c:5514 [inline]
> > hub_port_connect_change drivers/usb/core/hub.c:5725 [inline]
> > port_event drivers/usb/core/hub.c:5889 [inline]
> > hub_event+0x24e8/0x4d30 drivers/usb/core/hub.c:5971
> > process_one_work kernel/workqueue.c:3495 [inline]
> > process_scheduled_works+0xc3d/0x1630 kernel/workqueue.c:3578
> > worker_thread+0xa47/0xfb0 kernel/workqueue.c:3659
> > kthread+0x38b/0x480 kernel/kthread.c:436
> > ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
> >
> > Memory state around the buggy address:
> > ffff888035785a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff888035785a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > >ffff888035785b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ^
> > ffff888035785b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
> > ffff888035785c00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
> > ==================================================================
> >
> >
> > Tested on:
> >
> > commit: 8f7df005 Add linux-next specific files for 20261020
> > git tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
> > console output: https://syzkaller.appspot.com/x/log.txt?x=120a9fa9580000
> > kernel config: https://syzkaller.appspot.com/x/.config?x=9c1b9b13e3e4ce1a
> > dashboard link: https://syzkaller.appspot.com/bug?extid=809dfc586f33fc44b6ac
> > compiler: Debian clang version 22.1.8 (1~deb13u4), Debian LLD 22.1.8
> > patch: https://syzkaller.appspot.com/x/patch.diff?x=17b7b50d580000
> >
^ permalink raw reply [flat|nested] 5+ messages in thread
* Forwarded: [PATCH] media: em28xx: fix v4l2 use-after-free after failed init
2026-10-22 0:29 [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put syzbot
` (2 preceding siblings ...)
2026-10-22 16:17 ` syzbot
@ 2026-11-01 20:39 ` syzbot
3 siblings, 0 replies; 5+ messages in thread
From: syzbot @ 2026-11-01 20:39 UTC (permalink / raw)
To: linux-kernel
For archival purposes, forwarding an incoming command email to
linux-kernel@vger.kernel.org.
***
Subject: [PATCH] media: em28xx: fix v4l2 use-after-free after failed init
Author: drifabdelmalekmohamedsaid@gmail.com
#syz test
---
drivers/media/usb/em28xx/em28xx-video.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)
diff --git a/drivers/media/usb/em28xx/em28xx-video.c b/drivers/media/usb/em28xx/em28xx-video.c
index 84424284d486..924a3f7977c9 100644
--- a/drivers/media/usb/em28xx/em28xx-video.c
+++ b/drivers/media/usb/em28xx/em28xx-video.c
@@ -2414,7 +2414,7 @@ static int em28xx_v4l2_open(struct file *filp)
*/
static int em28xx_v4l2_fini(struct em28xx *dev)
{
- struct em28xx_v4l2 *v4l2 = dev->v4l2;
+ struct em28xx_v4l2 *v4l2;
if (dev->is_audio_only) {
/* Shouldn't initialize IR for this interface */
@@ -2426,13 +2426,17 @@ static int em28xx_v4l2_fini(struct em28xx *dev)
return 0;
}
- if (!v4l2)
- return 0;
-
dev_info(&dev->intf->dev, "Closing video extension\n");
mutex_lock(&dev->lock);
+ /* matches em28xx_v4l2_init error paths */
+ v4l2 = dev->v4l2;
+ if (!v4l2){
+ mutex_unlock(&dev->lock);
+ return 0;
+ }
+
v4l2_device_disconnect(&v4l2->v4l2_dev);
em28xx_uninit_usb_xfer(dev, EM28XX_ANALOG_MODE);
@@ -3129,6 +3133,9 @@ static int em28xx_v4l2_init(struct em28xx *dev)
vb2_video_unregister_device(&v4l2->vdev);
}
+ /* matches check in em28xx_v4l2_fini (under the same lock) */
+ dev->v4l2 = NULL;
+
mutex_unlock(&dev->lock);
/*
--
2.43.0
^ permalink raw reply related [flat|nested] 5+ messages in thread
end of thread, other threads:[~2026-11-01 20:39 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2026-10-22 0:29 [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put syzbot
2026-10-22 12:11 ` Forwarded: media: em28xx: fix refcount underflow caused by em28xx_free_v4l2 syzbot
2026-10-22 14:53 ` Forwarded: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put syzbot
2026-10-22 16:17 ` syzbot
2026-11-01 20:39 ` Forwarded: [PATCH] media: em28xx: fix v4l2 use-after-free after failed init syzbot
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