[syzbot] [media?] [usb?] kernel BUG in v4l2_device_put

[syzbot] [media?] [usb?] kernel BUG in v4l2_device_put

[syzbot]

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


---
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Forwarded: media: em28xx: fix refcount underflow caused by em28xx_free_v4l2

[syzbot]

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

Forwarded: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put

[syzbot]

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
>

Forwarded: Re: [syzbot] [media?] [usb?] kernel BUG in v4l2_device_put

[syzbot]

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
> >

Forwarded: [PATCH] media: em28xx: fix v4l2 use-after-free after failed init

[syzbot]

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

[syzbot] [media?] [usb?] KASAN: slab-use-after-free Read in v4l2_device_disconnect

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    4dd16e31135e Merge tag 'net-7.4-rc1' of git://git.kernel.o..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=15639629580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=119e5f4d0a8d39cf
dashboard link: https://syzkaller.appspot.com/bug?extid=1e71765881a6fc43185f
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=11a0808d580000

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/17a0632c09a1/disk-4dd16e31.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/d56bbd650c37/vmlinux-4dd16e31.xz
kernel image: https://storage.googleapis.com/syzbot-assets/83c14bba96f4/bzImage-4dd16e31.xz

AI-generated root cause summary:
In the em28xx driver, if initialization fails after video device nodes have been
registered, em28xx_v4l2_init() unregisters the nodes and drops its initial
reference on v4l2_dev without clearing dev->v4l2 to NULL. If a userspace process
has opened the video device node in the interim, the v4l2 instance remains
allocated until the file descriptor is closed. When the USB device is
disconnected or the extension is closed, em28xx_v4l2_fini() reads the non-NULL
dev->v4l2 pointer and concurrently attempts to disconnect and release the
already-destroyed or currently freeing v4l2_device, leading to a
slab-use-after-free in v4l2_device_disconnect().

full analysis:  https://syzkaller.appspot.com/x/ai_root_cause?x=1e71765881a6fc43185f

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1e71765881a6fc43185f@syzkaller.appspotmail.com

em28xx 2-1:0.191: Closing video extension
==================================================================
BUG: KASAN: slab-use-after-free in v4l2_device_disconnect+0xa4/0xc0 drivers/media/v4l2-core/v4l2-device.c:78
Read of size 8 at addr ffff88807de14008 by task kworker/1:1/29

CPU: 1 UID: 0 PID: 29 Comm: kworker/1:1 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
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/0x1c0 mm/kasan/report.c:595
 v4l2_device_disconnect+0xa4/0xc0 drivers/media/v4l2-core/v4l2-device.c:78
 em28xx_v4l2_fini.cold+0x65/0x312 drivers/media/usb/em28xx/em28xx-video.c:2436
 em28xx_close_extension+0xd2/0x460 drivers/media/usb/em28xx/em28xx-core.c:1262
 em28xx_usb_disconnect.cold+0x13d/0x253 drivers/media/usb/em28xx/em28xx-cards.c:4489
 usb_unbind_interface+0x1dd/0x9b0 drivers/usb/core/driver.c:460
 device_remove drivers/base/dd.c:619 [inline]
 device_remove+0x12a/0x180 drivers/base/dd.c:611
 __device_release_driver drivers/base/dd.c:1357 [inline]
 device_release_driver_internal+0x441/0x610 drivers/base/dd.c:1380
 bus_remove_device+0x2bc/0x560 drivers/base/bus.c:681
 device_del+0x376/0x9b0 drivers/base/core.c:3965
 usb_disable_device+0x367/0x810 drivers/usb/core/message.c:1484
 usb_disconnect+0x2e2/0x9a0 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+0x1bb1/0x4420 drivers/usb/core/hub.c:5971
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
 process_scheduled_works kernel/workqueue.c:3578 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
 </TASK>

Allocated by task 5952:
 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:409 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:426
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x2f8/0x6d0 mm/slub.c:5680
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 em28xx_v4l2_init.cold+0x94/0x3a7f drivers/media/usb/em28xx/em28xx-video.c:2751
 em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1245
 request_module_async+0x1e/0x30 drivers/media/usb/em28xx/em28xx-cards.c:3723
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
 process_scheduled_works kernel/workqueue.c:3578 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

Freed by task 7419:
 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:264 [inline]
 __kasan_slab_free+0x5f/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+0x22b/0x6d0 mm/slub.c:6923
 em28xx_free_v4l2+0x7b/0x110 drivers/media/usb/em28xx/em28xx-video.c:2337
 v4l2_device_release drivers/media/v4l2-core/v4l2-device.c:51 [inline]
 kref_put include/linux/kref.h:65 [inline]
 v4l2_device_put+0xa3/0xd0 drivers/media/v4l2-core/v4l2-device.c:56
 v4l2_device_release+0x2cf/0x480 drivers/media/v4l2-core/v4l2-dev.c:229
 device_release+0xd2/0x270 drivers/base/core.c:2640
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1f7/0x640 lib/kobject.c:737
 put_device+0x1f/0x30 drivers/base/core.c:3884
 video_put drivers/media/v4l2-core/v4l2-dev.c:173 [inline]
 v4l2_release+0x2da/0x390 drivers/media/v4l2-core/v4l2-dev.c:480
 __fput+0x3fb/0xb50 fs/file_table.c:512
 fput_close_sync+0x118/0x250 fs/file_table.c:618
 filp_close_sync+0x75/0xa0 fs/open.c:1573
 __do_sys_close fs/open.c:1596 [inline]
 __se_sys_close fs/open.c:1583 [inline]
 __x64_sys_close+0x81/0x110 fs/open.c:1583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The buggy address belongs to the object at ffff88807de14000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 8 bytes inside of
 freed 8192-byte region [ffff88807de14000, ffff88807de16000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x7de10
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 ffff88813ff0d280 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813ff0d280 dead000000000100 dead000000000122
head: 0000000000000000 0000000000020002 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 5287, tgid 5287 (dhcpcd-run-hook), ts 43652285249
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1856
 prep_new_page mm/page_alloc.c:1864 [inline]
 get_page_from_freelist+0x1113/0x35e0 mm/page_alloc.c:3935
 __alloc_frozen_pages_noprof+0x2bd/0x3280 mm/page_alloc.c:5444
 alloc_slab_page mm/slub.c:3384 [inline]
 allocate_slab mm/slub.c:3499 [inline]
 new_slab+0xb1/0x6d0 mm/slub.c:3550
 refill_objects+0xe3/0x410 mm/slub.c:7539
 refill_sheaf mm/slub.c:2917 [inline]
 __pcs_replace_empty_main+0x35e/0x650 mm/slub.c:4811
 alloc_from_pcs mm/slub.c:4887 [inline]
 slab_alloc_node mm/slub.c:5021 [inline]
 __kmalloc_cache_noprof+0x4ef/0x6d0 mm/slub.c:5676
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 tomoyo_print_bprm security/tomoyo/audit.c:26 [inline]
 tomoyo_init_log+0xb78/0x1f80 security/tomoyo/audit.c:262
 tomoyo_supervisor+0x506/0x1340 security/tomoyo/common.c:2232
 tomoyo_audit_path_log security/tomoyo/file.c:169 [inline]
 tomoyo_execute_permission+0x38e/0x4b0 security/tomoyo/file.c:624
 tomoyo_find_next_domain+0x38d/0x2010 security/tomoyo/domain.c:763
 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:834
 search_binary_handler fs/exec.c:1767 [inline]
 exec_binprm fs/exec.c:1809 [inline]
 bprm_execve fs/exec.c:1865 [inline]
 bprm_execve+0x80b/0x1940 fs/exec.c:1841
 do_execveat_common.isra.0+0x49d/0x580 fs/exec.c:1963
 __do_sys_execve fs/exec.c:2036 [inline]
 __se_sys_execve fs/exec.c:2030 [inline]
 __x64_sys_execve+0x93/0xd0 fs/exec.c:2030
page last free pid 5281 tgid 5281 ts 43568219751 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1403 [inline]
 __free_frozen_pages+0x7b4/0x1110 mm/page_alloc.c:2954
 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: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]
 __do_kmalloc_node mm/slub.c:5530 [inline]
 __kvmalloc_node_noprof+0x2f6/0x9b0 mm/slub.c:7136
 proc_sys_call_handler+0x2c7/0x5a0 fs/proc/proc_sysctl.c:583
 new_sync_write fs/read_write.c:595 [inline]
 vfs_write+0x6af/0x1050 fs/read_write.c:687
 ksys_write+0x12a/0x250 fs/read_write.c:739
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x123/0x790 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff88807de13f00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88807de13f80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88807de14000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                      ^
 ffff88807de14080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88807de14100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want syzbot to run the reproducer, reply with:
#syz test: git://repo/address.git branch-or-commit-hash
If you attach or paste a git patch, syzbot will apply it before testing.

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup

Forwarded: [PATCH] media: em28xx: fix v4l2 use-after-free after failed init

[syzbot]

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

[syzbot] [media?] [usb?] KASAN: slab-use-after-free Read in dev_dbg_obj

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    cbbddb6b08cc Merge tag 'power-utilities-2026.10.31' of git..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11fc0581580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=bd712e5dbce1d1a0
dashboard link: https://syzkaller.appspot.com/bug?extid=54648a6c1187a7ef46a6
compiler:       gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
userspace arch: i386
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12f0e62d580000

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-cbbddb6b.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/4e9212cb9d41/vmlinux-cbbddb6b.xz
kernel image: https://storage.googleapis.com/syzbot-assets/b7710a90cc0c/bzImage-cbbddb6b.xz

AI-generated root cause summary:
In drivers/media/usb/em28xx/em28xx-video.c, if em28xx_v4l2_init() fails after
registering video devices (e.g. during v4l2_mc_create_media_graph()) while
userspace concurrently holds an open file handle to a video device node,
unregister_dev drops the initial v4l2_dev reference but leaves dev->v4l2
non-NULL. When the device disconnects, em28xx_v4l2_fini() is called and
incorrectly drops the initial reference a second time via
v4l2_device_put(&v4l2->v4l2_dev). This refcount underflow causes
em28xx_free_v4l2() to free struct em28xx_v4l2 prematurely, resulting in a slab
use-after-free when userspace closes the file descriptor and
v4l2_device_release() accesses embedded media entities.

full analysis:  https://syzkaller.appspot.com/x/ai_root_cause?x=54648a6c1187a7ef46a6

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+54648a6c1187a7ef46a6@syzkaller.appspotmail.com

==================================================================
BUG: KASAN: slab-use-after-free in media_type include/media/media-entity.h:443 [inline]
BUG: KASAN: slab-use-after-free in dev_dbg_obj+0x630/0x830 drivers/media/mc/mc-entity.c:96
Read of size 4 at addr ffff888023601bd0 by task v4l_id/6384

CPU: 2 UID: 0 PID: 6384 Comm: v4l_id Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014
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/0x1c0 mm/kasan/report.c:595
 media_type include/media/media-entity.h:443 [inline]
 dev_dbg_obj+0x630/0x830 drivers/media/mc/mc-entity.c:96
 media_gobj_destroy drivers/media/mc/mc-entity.c:179 [inline]
 media_gobj_destroy+0x4d/0x240 drivers/media/mc/mc-entity.c:173
 __media_device_unregister_entity+0x20c/0x2f0 drivers/media/mc/mc-device.c:597
 media_device_unregister_entity+0x4b/0x70 drivers/media/mc/mc-device.c:677
 v4l2_device_release+0x363/0x480 drivers/media/v4l2-core/v4l2-dev.c:208
 device_release+0xd2/0x270 drivers/base/core.c:2640
 kobject_cleanup lib/kobject.c:689 [inline]
 kobject_release lib/kobject.c:720 [inline]
 kref_put include/linux/kref.h:65 [inline]
 kobject_put+0x1f7/0x640 lib/kobject.c:737
 put_device+0x1f/0x30 drivers/base/core.c:3886
 video_put drivers/media/v4l2-core/v4l2-dev.c:173 [inline]
 v4l2_release+0x2da/0x390 drivers/media/v4l2-core/v4l2-dev.c:480
 __fput+0x3fb/0xb50 fs/file_table.c:512
 fput_close_sync+0x118/0x250 fs/file_table.c:618
 filp_close_sync+0x75/0xa0 fs/open.c:1573
 __do_sys_close fs/open.c:1596 [inline]
 __se_sys_close fs/open.c:1583 [inline]
 __x64_sys_close+0x81/0x110 fs/open.c:1583
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x121/0x770 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fb504ca7407
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:00007ffe26ad6260 EFLAGS: 00000202 ORIG_RAX: 0000000000000003
RAX: ffffffffffffffda RBX: 00007fb5053c2880 RCX: 00007fb504ca7407
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00007fb5053c26e8 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000013
R13: 00007ffe26ad6490 R14: 00007fb505529000 R15: 0000564e446754d8
 </TASK>

Allocated by task 34:
 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:409 [inline]
 __kasan_kmalloc+0xaa/0xb0 mm/kasan/common.c:426
 kasan_kmalloc include/linux/kasan.h:263 [inline]
 __kmalloc_cache_noprof+0x2f8/0x6d0 mm/slub.c:5680
 _kmalloc_noprof include/linux/slab.h:991 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 em28xx_v4l2_init.cold+0x94/0x3a7f drivers/media/usb/em28xx/em28xx-video.c:2751
 em28xx_init_extension+0x13a/0x200 drivers/media/usb/em28xx/em28xx-core.c:1245
 request_module_async+0x1e/0x30 drivers/media/usb/em28xx/em28xx-cards.c:3723
 process_one_work+0xac7/0x1b10 kernel/workqueue.c:3495
 process_scheduled_works kernel/workqueue.c:3578 [inline]
 worker_thread+0x5ef/0xe50 kernel/workqueue.c:3659
 kthread+0x373/0x450 kernel/kthread.c:436
 ret_from_fork+0x730/0xd60 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 ffff888023600000
 which belongs to the cache kmalloc-8k of size 8192
The buggy address is located 7120 bytes inside of
 freed 8192-byte region [ffff888023600000, ffff888023602000)

The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x23600
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 ffff88801d443180 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000020002 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88801d443180 dead000000000100 dead000000000122
head: 0000000000000000 0000000000020002 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 0xd20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC), pid 5812, tgid 5812 (syz-executor), ts 73629010596
 set_page_owner include/linux/page_owner.h:33 [inline]
 post_alloc_hook+0xfd/0x120 mm/page_alloc.c:1856
 prep_new_page mm/page_alloc.c:1864 [inline]
 get_page_from_freelist+0x1113/0x35e0 mm/page_alloc.c:3935
 __alloc_frozen_pages_noprof+0x2bd/0x3280 mm/page_alloc.c:5444
 alloc_slab_page mm/slub.c:3384 [inline]
 allocate_slab mm/slub.c:3499 [inline]
 new_slab+0xb1/0x6d0 mm/slub.c:3550
 refill_objects+0xe3/0x410 mm/slub.c:7539
 refill_sheaf mm/slub.c:2917 [inline]
 __pcs_replace_empty_main+0x35e/0x650 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+0x677/0x840 mm/slub.c:5556
 _kmalloc_noprof include/linux/slab.h:995 [inline]
 _kzalloc_noprof include/linux/slab.h:1312 [inline]
 ops_init+0x77/0x5f0 net/core/net_namespace.c:127
 setup_net+0x118/0x3a0 net/core/net_namespace.c:443
 copy_net_ns+0x340/0x7a0 net/core/net_namespace.c:584
 create_new_namespaces+0x3ea/0xac0 kernel/nsproxy.c:132
 unshare_nsproxy_namespaces+0xf6/0x210 kernel/nsproxy.c:234
 ksys_unshare+0x44f/0x980 kernel/fork.c:3298
 __do_sys_unshare kernel/fork.c:3364 [inline]
 __se_sys_unshare kernel/fork.c:3362 [inline]
 __ia32_sys_unshare+0x30/0x40 kernel/fork.c:3362
 do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:79 [inline]
 __do_fast_syscall_32+0x14b/0x8c0 arch/x86/entry/syscall_32.c:282
 do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:307
page last free pid 5501 tgid 5501 ts 24218447288 stack trace:
 reset_page_owner include/linux/page_owner.h:26 [inline]
 __free_pages_prepare mm/page_alloc.c:1403 [inline]
 __free_frozen_pages+0x7b4/0x1110 mm/page_alloc.c:2954
 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: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]
 kmem_cache_alloc_node_noprof+0x282/0x6e0 mm/slub.c:5105
 __alloc_skb+0x140/0x710 net/core/skbuff.c:705
 alloc_skb include/linux/skbuff.h:1390 [inline]
 alloc_skb_with_frags+0xdb/0x750 net/core/skbuff.c:6898
 sock_alloc_send_pskb+0x86a/0x9e0 net/core/sock.c:3093
 unix_dgram_sendmsg+0x3f4/0x1a80 net/unix/af_unix.c:2148
 unix_seqpacket_sendmsg+0x12a/0x1d0 net/unix/af_unix.c:2549
 sock_sendmsg_nosec net/socket.c:800 [inline]
 __sock_sendmsg net/socket.c:818 [inline]
 sock_write_iter+0x560/0x5d0 net/socket.c:1269
 do_iter_readv_writev+0x6f7/0x930 fs/read_write.c:828
 vfs_writev+0x360/0xdd0 fs/read_write.c:1058
 do_writev+0x28a/0x340 fs/read_write.c:1104
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x121/0x770 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Memory state around the buggy address:
 ffff888023601a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888023601b00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888023601b80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                 ^
 ffff888023601c00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888023601c80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================


---
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Forwarded: [PATCH] media: em28xx: fix v4l2 use-after-free after failed init

[syzbot]

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