possible deadlock in uvcg_frame_dw_frame_interval_store

Status: upstream: reported on 2026/08/17 15:39
Reported-by: syzbot+9e7b9ab5531353749852@syzkaller.appspotmail.com
First crash: 8d17h, last: 2d14h
▶ ▼ Similar bugs (2)
Kernel Title Rank 🛈 Repro Cause bisect Fix bisect Count Last Reported Patched Status
linux-6.1 possible deadlock in uvcg_frame_dw_frame_interval_store 4 1 4d21h 4d21h 0/3 upstream: reported on 2026/08/21 11:12
upstream possible deadlock in uvcg_frame_dw_frame_interval_store usb prio:low 4 3 3d09h 12d 0/29 upstream: reported on 2026/08/13 11:09

Sample crash report:
======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.2.197/5134 is trying to acquire lock:
ffffffff8cece4d0 (gadget_subsys.su_mutex){+.+.}-{3:3}, at: uvcg_frame_dw_frame_interval_store+0xde/0x9c0 drivers/usb/gadget/function/uvc_configfs.c:1336

but task is already holding lock:
ffff88802b2cc778 (&p->frag_sem){++++}-{3:3}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
ffff88802b2cc778 (&p->frag_sem){++++}-{3:3}, at: configfs_write_iter+0x20e/0x400 fs/configfs/file.c:229

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&p->frag_sem){++++}-{3:3}:
       down_write_killable+0x46/0x90 kernel/locking/rwsem.c:1562
       configfs_rmdir+0x3e0/0x980 fs/configfs/dir.c:1534
       vfs_rmdir+0x19d/0x410 fs/namei.c:4200
       do_rmdir+0x27f/0x710 fs/namei.c:4261
       __do_sys_unlinkat fs/namei.c:4441 [inline]
       __se_sys_unlinkat fs/namei.c:4435 [inline]
       __x64_sys_unlinkat+0xc0/0xe0 fs/namei.c:4435
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #2 (&sb->s_type->i_mutex_key#24){++++}-{3:3}:
       down_write+0x38/0x60 kernel/locking/rwsem.c:1551
       inode_lock include/linux/fs.h:793 [inline]
       configfs_depend_item_unlocked+0x14f/0x430 fs/configfs/dir.c:1255
       usbg_make_tpg+0x1f3/0x580 drivers/usb/gadget/function/f_tcm.c:1351
       target_fabric_make_tpg+0xa0/0x6d0 drivers/target/target_core_fabric_configfs.c:837
       configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x386/0x570 fs/namei.c:4116
       do_mkdirat+0x1dd/0x5c0 fs/namei.c:4141
       __do_sys_mkdir fs/namei.c:4161 [inline]
       __se_sys_mkdir fs/namei.c:4159 [inline]
       __x64_sys_mkdir+0x6a/0x80 fs/namei.c:4159
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #1 (&opts->dep_lock){+.+.}-{3:3}:
       __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       tcm_set_name+0x26/0x90 drivers/usb/gadget/function/f_tcm.c:2353
       function_make+0x195/0x350 drivers/usb/gadget/configfs.c:620
       configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x386/0x570 fs/namei.c:4116
       do_mkdirat+0x1dd/0x5c0 fs/namei.c:4141
       __do_sys_mkdir fs/namei.c:4161 [inline]
       __se_sys_mkdir fs/namei.c:4159 [inline]
       __x64_sys_mkdir+0x6a/0x80 fs/namei.c:4159
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

-> #0 (gadget_subsys.su_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3053 [inline]
       check_prevs_add kernel/locking/lockdep.c:3172 [inline]
       validate_chain kernel/locking/lockdep.c:3788 [inline]
       __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
       lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
       __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
       __mutex_lock kernel/locking/mutex.c:729 [inline]
       mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
       uvcg_frame_dw_frame_interval_store+0xde/0x9c0 drivers/usb/gadget/function/uvc_configfs.c:1336
       flush_write_buffer fs/configfs/file.c:207 [inline]
       configfs_write_iter+0x30b/0x400 fs/configfs/file.c:229
       call_write_iter include/linux/fs.h:2179 [inline]
       new_sync_write fs/read_write.c:507 [inline]
       vfs_write+0x748/0xd70 fs/read_write.c:594
       ksys_write+0x153/0x260 fs/read_write.c:647
       do_syscall_x64 arch/x86/entry/common.c:50 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
       entry_SYSCALL_64_after_hwframe+0x66/0xd0

other info that might help us debug this:

Chain exists of:
  gadget_subsys.su_mutex --> &sb->s_type->i_mutex_key#24 --> &p->frag_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&p->frag_sem);
                               lock(&sb->s_type->i_mutex_key#24);
                               lock(&p->frag_sem);
  lock(gadget_subsys.su_mutex);

 *** DEADLOCK ***

4 locks held by syz.2.197/5134:
 #0: ffff88802ceac870 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2bf/0x370 fs/file.c:1056
 #1: ffff88801dd10460 (sb_writers#15){.+.+}-{0:0}, at: vfs_write+0x296/0xd70 fs/read_write.c:590
 #2: ffff888079708488 (&buffer->mutex){+.+.}-{3:3}, at: configfs_write_iter+0x7d/0x400 fs/configfs/file.c:226
 #3: ffff88802b2cc778 (&p->frag_sem){++++}-{3:3}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
 #3: ffff88802b2cc778 (&p->frag_sem){++++}-{3:3}, at: configfs_write_iter+0x20e/0x400 fs/configfs/file.c:229

stack backtrace:
CPU: 0 PID: 5134 Comm: syz.2.197 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x250 lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2133
 check_prev_add kernel/locking/lockdep.c:3053 [inline]
 check_prevs_add kernel/locking/lockdep.c:3172 [inline]
 validate_chain kernel/locking/lockdep.c:3788 [inline]
 __lock_acquire+0x2c66/0x7b50 kernel/locking/lockdep.c:5012
 lock_acquire+0x19e/0x400 kernel/locking/lockdep.c:5623
 __mutex_lock_common+0x1e5/0x2400 kernel/locking/mutex.c:596
 __mutex_lock kernel/locking/mutex.c:729 [inline]
 mutex_lock_nested+0x17/0x20 kernel/locking/mutex.c:743
 uvcg_frame_dw_frame_interval_store+0xde/0x9c0 drivers/usb/gadget/function/uvc_configfs.c:1336
 flush_write_buffer fs/configfs/file.c:207 [inline]
 configfs_write_iter+0x30b/0x400 fs/configfs/file.c:229
 call_write_iter include/linux/fs.h:2179 [inline]
 new_sync_write fs/read_write.c:507 [inline]
 vfs_write+0x748/0xd70 fs/read_write.c:594
 ksys_write+0x153/0x260 fs/read_write.c:647
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x66/0xd0
RIP: 0033:0x7fd2b50a70d9
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:00007fd2b32ff028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007fd2b532efa0 RCX: 00007fd2b50a70d9
RDX: 0000000000000007 RSI: 0000200000000540 RDI: 0000000000000006
RBP: 00007fd2b513e024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007fd2b532f038 R14: 00007fd2b532efa0 R15: 00007ffed9506c88
 </TASK>

Crashes (2):
Time Kernel Commit Syzkaller Config Log Report Syz repro C repro VM info Assets (help?) Manager Title
2026/08/23 19:03 linux-5.15.y 945fa863f02c 1e72964b .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in uvcg_frame_dw_frame_interval_store
2026/08/17 15:38 linux-5.15.y aabd761612db 905244d6 .config console log report info [disk image] [vmlinux] [kernel image] ci2-linux-5-15-kasan possible deadlock in uvcg_frame_dw_frame_interval_store
* Struck through repros no longer work on HEAD.