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 08:40:01 -0700 [thread overview]
Message-ID: <6ada2e51.4c8f3b9a.1a805.0093.GAE@google.com> (raw)
In-Reply-To: <CAFJkwZzN_bRRY4hqa1upEsCmnXyMeYdUd-4dKhO9_8vvuwVc4g@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 em28xx_write_regs_req
==================================================================
BUG: KASAN: slab-use-after-free in __intf_to_usbdev include/linux/usb.h:752 [inline]
BUG: KASAN: slab-use-after-free in em28xx_write_regs_req+0x79/0x3c0 drivers/media/usb/em28xx/em28xx-core.c:138
Read of size 8 at addr ffff88802229e0b8 by task v4l_id/8728
CPU: 0 UID: 0 PID: 8728 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
__intf_to_usbdev include/linux/usb.h:752 [inline]
em28xx_write_regs_req+0x79/0x3c0 drivers/media/usb/em28xx/em28xx-core.c:138
em28xx_write_regs drivers/media/usb/em28xx/em28xx-core.c:179 [inline]
em28xx_write_reg+0x89/0xd0 drivers/media/usb/em28xx/em28xx-core.c:186
em28xx_set_outfmt+0xb1/0x420 drivers/media/usb/em28xx/em28xx-video.c:233
em28xx_resolution_set+0x261/0x7f0 drivers/media/usb/em28xx/em28xx-video.c:339
em28xx_v4l2_open+0x21a/0x840 drivers/media/usb/em28xx/em28xx-video.c:2390
v4l2_open+0x1bc/0x3a0 drivers/media/v4l2-core/v4l2-dev.c:433
chrdev_open+0x4d9/0x600 fs/char_dev.c:413
do_dentry_open+0x80e/0x1360 fs/open.c:1000
vfs_open_consume+0x4a/0x350 fs/open.c:1131
do_open fs/namei.c:4845 [inline]
path_openat+0x16fc/0x20f0 fs/namei.c:5010
do_file_open+0x23e/0x4a0 fs/namei.c:5039
do_sys_openat2+0x115/0x200 fs/open.c:1442
do_sys_open fs/open.c:1448 [inline]
__do_sys_openat fs/open.c:1788 [inline]
__se_sys_openat fs/open.c:1783 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1783
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: 0033:0x7fc4a0ea7407
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:00007ffee11a62b0 EFLAGS: 00000202 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fc4a1572880 RCX: 00007fc4a0ea7407
RDX: 0000000000000000 RSI: 00007ffee11a7f1d RDI: ffffffffffffff9c
RBP: 0000000000000002 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000
R13: 00007ffee11a6500 R14: 00007fc4a1677000 R15: 000055b0a97fd4d8
</TASK>
Allocated by task 3215:
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]
usb_set_configuration+0x3c5/0x2260 drivers/usb/core/message.c:2103
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 3215:
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
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
usb_disable_device+0x611/0x8d0 drivers/usb/core/message.c:1491
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 ffff88802229e000
which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 184 bytes inside of
freed 2048-byte region [ffff88802229e000, ffff88802229e800)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x22298
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 ffff88813ff30000 dead000000000100 dead000000000122
raw: 0000000000000000 0000000000080008 00000000f5000000 0000000000000000
head: 00fff00000000040 ffff88813ff30000 dead000000000100 dead000000000122
head: 0000000000000000 0000000000080008 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 1, tgid 1 (swapper/0), ts 5001221219
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]
__kmalloc_cache_noprof+0x396/0x600 mm/slub.c:5676
_kmalloc_noprof include/linux/slab.h:991 [inline]
_kzalloc_noprof include/linux/slab.h:1312 [inline]
acpi_add_single_object+0xdb/0x1b30 drivers/acpi/scan.c:1870
acpi_bus_check_add+0x2b5/0x840 drivers/acpi/scan.c:2175
acpi_ns_walk_namespace+0x273/0x700 drivers/acpi/acpica/nswalk.c:-1
acpi_walk_namespace+0x125/0x190 drivers/acpi/acpica/nsxfeval.c:606
acpi_bus_scan+0xe9/0x4b0 drivers/acpi/scan.c:2732
acpi_scan_init+0x1bd/0x4e0 drivers/acpi/scan.c:2873
acpi_init+0x130/0x1f0 drivers/acpi/bus.c:1483
do_one_initcall+0x250/0x870 init/main.c:1419
do_initcall_level+0x10a/0x1a0 init/main.c:1481
page last free pid 1 tgid 1 ts 3782412345 stack trace:
reset_page_owner include/linux/page_owner.h:26 [inline]
__free_pages_prepare mm/page_alloc.c:1403 [inline]
__free_pages_ok+0xb6d/0xc60 mm/page_alloc.c:1581
btf_add_type kernel/bpf/btf.c:1782 [inline]
btf_check_all_metas+0x5e7/0xa30 kernel/bpf/btf.c:5888
btf_parse_base kernel/bpf/btf.c:6883 [inline]
btf_parse_vmlinux+0x51d/0x8c0 kernel/bpf/btf.c:6917
bpf_get_btf_vmlinux+0x48/0x70 kernel/bpf/verifier.c:23010
btf_get_module_btf kernel/bpf/btf.c:9601 [inline]
__register_btf_kfunc_id_set+0x62/0x14c0 kernel/bpf/btf.c:10122
wakeup_sources_bpf_init+0x11/0x60 drivers/base/power/wakeup.c:1229
wakeup_sources_init+0x28/0x30 drivers/base/power/wakeup.c:1240
do_one_initcall+0x250/0x870 init/main.c:1419
do_initcall_level+0x10a/0x1a0 init/main.c:1481
do_initcalls+0x59/0xa0 init/main.c:1497
kernel_init_freeable+0x29d/0x3e0 init/main.c:1732
kernel_init+0x22/0x1d0 init/main.c:1622
ret_from_fork+0x514/0xb70 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245
Memory state around the buggy address:
ffff88802229df80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff88802229e000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff88802229e080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
^
ffff88802229e100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
ffff88802229e180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
==================================================================
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=16626e7f980000
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=1232a3cd580000
next parent reply other threads:[~2026-10-22 15:40 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CAFJkwZzN_bRRY4hqa1upEsCmnXyMeYdUd-4dKhO9_8vvuwVc4g@mail.gmail.com>
2026-10-22 15:40 ` syzbot [this message]
[not found] <CAFJkwZzqQtu6K7xYdJMp8Wm3DEa-Psp4tiyPxi_H=gcWygT6uA@mail.gmail.com>
2026-10-22 16:58 ` syzbot
[not found] <CAFJkwZzx+CfBNYxfzToB-0iKrr1=MB6bxh8ySU7uApxyQXm-PA@mail.gmail.com>
2026-10-22 14:08 ` syzbot
2026-10-22 0:29 syzbot
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