From: syzbot <syzbot+809dfc586f33fc44b6ac@syzkaller.appspotmail.com>
To: linux-kernel@vger.kernel.org, neganhat@gmail.com,
syzkaller-bugs@googlegroups.com
Subject: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put
Date: Thu, 22 Oct 2026 07:08:02 -0700 [thread overview]
Message-ID: <6ada18c2.4c8f3b9a.1a805.0078.GAE@google.com> (raw)
In-Reply-To: <CAFJkwZzx+CfBNYxfzToB-0iKrr1=MB6bxh8ySU7uApxyQXm-PA@mail.gmail.com>
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
next parent reply other threads:[~2026-10-22 14:08 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAFJkwZzx+CfBNYxfzToB-0iKrr1=MB6bxh8ySU7uApxyQXm-PA@mail.gmail.com>
2026-10-22 14:08 ` syzbot [this message]
[not found] <CAFJkwZzqQtu6K7xYdJMp8Wm3DEa-Psp4tiyPxi_H=gcWygT6uA@mail.gmail.com>
2026-10-22 16:58 ` syzbot
[not found] <CAFJkwZzN_bRRY4hqa1upEsCmnXyMeYdUd-4dKhO9_8vvuwVc4g@mail.gmail.com>
2026-10-22 15:40 ` syzbot
2026-10-22 0:29 syzbot
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