From: syzbot <syzbot+2b082cefcfb1439289ef@syzkaller.appspotmail.com>
To: a.hindborg@kernel.org, leitao@debian.org,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
syzkaller-bugs@googlegroups.com
Subject: [syzbot] [fs?] possible deadlock in uvcg_mjpeg_bma_controls_show
Date: Tue, 18 Aug 2026 01:56:32 -0700 [thread overview]
Message-ID: <6a841e40.c8649fcc.3bb87.0003.GAE@google.com> (raw)
Hello,
syzbot found the following issue on:
HEAD commit: 8d3ae59288f1 Linux 7.2
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=10b1d69e580000
kernel config: https://syzkaller.appspot.com/x/.config?x=2ca5f2f2c4197664
dashboard link: https://syzkaller.appspot.com/bug?extid=2b082cefcfb1439289ef
compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8
Unfortunately, I don't have any reproducer for this issue yet.
Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/79f5b21ede1d/disk-8d3ae592.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/0f43313295ab/vmlinux-8d3ae592.xz
kernel image: https://storage.googleapis.com/syzbot-assets/5de229a3986e/bzImage-8d3ae592.xz
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+2b082cefcfb1439289ef@syzkaller.appspotmail.com
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz.9.535/9115 is trying to acquire lock:
ffffffff8f9eb768 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_format_bma_controls_show drivers/usb/gadget/function/uvc_configfs.c:1681 [inline]
ffffffff8f9eb768 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_mjpeg_bma_controls_show+0x4d/0x140 drivers/usb/gadget/function/uvc_configfs.c:2635
but task is already holding lock:
ffff88803207b570 (&p->frag_sem){++++}-{4:4}, at: fill_read_buffer fs/configfs/file.c:66 [inline]
ffff88803207b570 (&p->frag_sem){++++}-{4:4}, at: configfs_read_iter+0x1cc/0x620 fs/configfs/file.c:88
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #3 (&p->frag_sem){++++}-{4:4}:
down_write_killable+0xa6/0x240 kernel/locking/rwsem.c:1643
configfs_rmdir+0x3b0/0x950 fs/configfs/dir.c:1534
vfs_rmdir+0x3e6/0x6a0 fs/namei.c:5381
filename_rmdir+0x292/0x520 fs/namei.c:5438
__do_sys_unlinkat fs/namei.c:5613 [inline]
__se_sys_unlinkat+0x71/0x1a0 fs/namei.c:5606
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #2 (&sb->s_type->i_mutex_key#27){++++}-{4:4}:
down_write+0x96/0x200 kernel/locking/rwsem.c:1631
inode_lock include/linux/fs.h:1024 [inline]
configfs_depend_item_unlocked+0x153/0x420 fs/configfs/dir.c:1259
usbg_make_tpg+0x1f6/0x590 drivers/usb/gadget/function/f_tcm.c:1686
target_fabric_make_tpg+0xa8/0x6d0 drivers/target/target_core_fabric_configfs.c:939
configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x406/0x620 fs/namei.c:5276
filename_mkdirat+0x285/0x510 fs/namei.c:5309
__do_sys_mkdirat fs/namei.c:5330 [inline]
__se_sys_mkdirat+0x35/0x150 fs/namei.c:5327
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #1 (&opts->dep_lock){+.+.}-{4:4}:
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
tcm_set_name+0x2b/0xd0 drivers/usb/gadget/function/f_tcm.c:2669
function_make+0x1a8/0x360 drivers/usb/gadget/configfs.c:636
configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1360
vfs_mkdir+0x406/0x620 fs/namei.c:5276
filename_mkdirat+0x285/0x510 fs/namei.c:5309
__do_sys_mkdirat fs/namei.c:5330 [inline]
__se_sys_mkdirat+0x35/0x150 fs/namei.c:5327
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
-> #0 (gadget_subsys.su_mutex){+.+.}-{4:4}:
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
uvcg_format_bma_controls_show drivers/usb/gadget/function/uvc_configfs.c:1681 [inline]
uvcg_mjpeg_bma_controls_show+0x4d/0x140 drivers/usb/gadget/function/uvc_configfs.c:2635
fill_read_buffer fs/configfs/file.c:68 [inline]
configfs_read_iter+0x2b7/0x620 fs/configfs/file.c:88
__kernel_read+0x4ca/0x960 fs/read_write.c:532
integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
ima_calc_file_hash+0x451/0x890 security/integrity/ima/ima_crypto.c:280
ima_collect_measurement+0x51b/0xa00 security/integrity/ima/ima_api.c:300
process_measurement+0x1272/0x1c10 security/integrity/ima/ima_main.c:425
ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
security_file_post_open+0xb3/0x260 security/security.c:2755
do_open fs/namei.c:4702 [inline]
path_openat+0x2e90/0x3830 fs/namei.c:4863
do_file_open+0x23e/0x4a0 fs/namei.c:4892
do_sys_openat2+0x115/0x200 fs/open.c:1368
do_sys_open fs/open.c:1374 [inline]
__do_sys_openat fs/open.c:1390 [inline]
__se_sys_openat fs/open.c:1385 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1385
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
other info that might help us debug this:
Chain exists of:
gadget_subsys.su_mutex --> &sb->s_type->i_mutex_key#27 --> &p->frag_sem
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
rlock(&p->frag_sem);
lock(&sb->s_type->i_mutex_key#27);
lock(&p->frag_sem);
lock(gadget_subsys.su_mutex);
*** DEADLOCK ***
3 locks held by syz.9.535/9115:
#0: ffff88807ddab480 (&ima_iint_mutex_key[depth]){+.+.}-{4:4}, at: process_measurement+0x7d0/0x1c10 security/integrity/ima/ima_main.c:319
#1: ffff88801f7dd080 (&buffer->mutex){+.+.}-{4:4}, at: configfs_read_iter+0x70/0x620 fs/configfs/file.c:86
#2: ffff88803207b570 (&p->frag_sem){++++}-{4:4}, at: fill_read_buffer fs/configfs/file.c:66 [inline]
#2: ffff88803207b570 (&p->frag_sem){++++}-{4:4}, at: configfs_read_iter+0x1cc/0x620 fs/configfs/file.c:88
stack backtrace:
CPU: 0 UID: 0 PID: 9115 Comm: syz.9.535 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
Call Trace:
<TASK>
dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
print_circular_bug+0x2e1/0x300 kernel/locking/lockdep.c:2043
check_noncircular+0x12e/0x150 kernel/locking/lockdep.c:2175
check_prev_add kernel/locking/lockdep.c:3165 [inline]
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x1520/0x2cf0 kernel/locking/lockdep.c:5237
lock_acquire+0x106/0x350 kernel/locking/lockdep.c:5868
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
uvcg_format_bma_controls_show drivers/usb/gadget/function/uvc_configfs.c:1681 [inline]
uvcg_mjpeg_bma_controls_show+0x4d/0x140 drivers/usb/gadget/function/uvc_configfs.c:2635
fill_read_buffer fs/configfs/file.c:68 [inline]
configfs_read_iter+0x2b7/0x620 fs/configfs/file.c:88
__kernel_read+0x4ca/0x960 fs/read_write.c:532
integrity_kernel_read+0x89/0xd0 security/integrity/iint.c:28
ima_calc_file_hash_tfm security/integrity/ima/ima_crypto.c:222 [inline]
ima_calc_file_hash+0x451/0x890 security/integrity/ima/ima_crypto.c:280
ima_collect_measurement+0x51b/0xa00 security/integrity/ima/ima_api.c:300
process_measurement+0x1272/0x1c10 security/integrity/ima/ima_main.c:425
ima_file_check+0xe1/0x130 security/integrity/ima/ima_main.c:685
security_file_post_open+0xb3/0x260 security/security.c:2755
do_open fs/namei.c:4702 [inline]
path_openat+0x2e90/0x3830 fs/namei.c:4863
do_file_open+0x23e/0x4a0 fs/namei.c:4892
do_sys_openat2+0x115/0x200 fs/open.c:1368
do_sys_open fs/open.c:1374 [inline]
__do_sys_openat fs/open.c:1390 [inline]
__se_sys_openat fs/open.c:1385 [inline]
__x64_sys_openat+0x138/0x170 fs/open.c:1385
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x174/0x580 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fc9faf9e0d9
Code: ff c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 e8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fc9fbdd8028 EFLAGS: 00000246 ORIG_RAX: 0000000000000101
RAX: ffffffffffffffda RBX: 00007fc9fb226180 RCX: 00007fc9faf9e0d9
RDX: 0000000000000002 RSI: 00002000000002c0 RDI: ffffffffffffff9c
RBP: 00007fc9fb035024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fc9fb226218 R14: 00007fc9fb226180 R15: 00007ffe7532db78
</TASK>
---
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 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
reply other threads:[~2026-08-18 8:56 UTC|newest]
Thread overview: [no followups] expand[flat|nested] mbox.gz Atom feed
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=6a841e40.c8649fcc.3bb87.0003.GAE@google.com \
--to=syzbot+2b082cefcfb1439289ef@syzkaller.appspotmail.com \
--cc=a.hindborg@kernel.org \
--cc=leitao@debian.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=syzkaller-bugs@googlegroups.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox