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

[syzbot <syzbot+809dfc586f33fc44b6ac@syzkaller.appspotmail.com>]

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***

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
>