[syzbot] [usb?] possible deadlock in uvcg_frame_dw_frame_interval_store

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 06cf61899d64 Merge tag 'x86-urgent-2026-08-08' of git://gi..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=13484149580000
kernel config: https://syzkaller.appspot.com/x/.config?x=8a233ed2ce9a8096
dashboard link: https://syzkaller.appspot.com/bug?extid=b37b42183fe588ceeb88
compiler: gcc (Debian 14.2.0-19) 14.2.0, GNU ld (GNU Binutils for Debian) 2.44
userspace arch: i386

Unfortunately, I don't have any reproducer for this issue yet.

Downloadable assets:
disk image (non-bootable): https://storage.googleapis.com/syzbot-assets/d900f083ada3/non_bootable_disk-06cf6189.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/1a9de4812597/vmlinux-06cf6189.xz
kernel image: https://storage.googleapis.com/syzbot-assets/e873dfe980ea/bzImage-06cf6189.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+b37b42...@syzkaller.appspotmail.com

======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G L
------------------------------------------------------
syz.0.2631/16146 is trying to acquire lock:
ffffffff901cc668 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_frame_dw_frame_interval_store+0xdf/0x4b0 drivers/usb/gadget/function/uvc_configfs.c:2076

but task is already holding lock:
ffff8880275d5170 (&p->frag_sem){++++}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
ffff8880275d5170 (&p->frag_sem){++++}-{4:4}, at: configfs_write_iter+0x218/0x4e0 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){++++}-{4:4}:
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
down_write_killable+0x93/0x250 kernel/locking/rwsem.c:1643
configfs_rmdir+0x3fa/0x950 fs/configfs/dir.c:1534
vfs_rmdir fs/namei.c:5381 [inline]
vfs_rmdir+0x328/0x8a0 fs/namei.c:5354
filename_rmdir+0x31a/0x5c0 fs/namei.c:5438
__do_sys_unlinkat fs/namei.c:5613 [inline]
__se_sys_unlinkat fs/namei.c:5606 [inline]
__ia32_sys_unlinkat+0xf5/0x130 fs/namei.c:5606
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

-> #2 (&sb->s_type->i_mutex_key#24){++++}-{4:4}:
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
down_write+0x8b/0x1f0 kernel/locking/rwsem.c:1631
inode_lock include/linux/fs.h:1024 [inline]
configfs_depend_item_unlocked+0xf3/0x6a0 fs/configfs/dir.c:1259
usbg_make_tpg+0x261/0x620 drivers/usb/gadget/function/f_tcm.c:1686
target_fabric_make_tpg+0xab/0x8c0 drivers/target/target_core_fabric_configfs.c:939
configfs_mkdir+0x51e/0xb70 fs/configfs/dir.c:1360
vfs_mkdir+0x361/0x850 fs/namei.c:5276
filename_mkdirat+0x48b/0x5e0 fs/namei.c:5309
__do_sys_mkdir fs/namei.c:5336 [inline]
__se_sys_mkdir fs/namei.c:5333 [inline]
__ia32_sys_mkdir+0x6a/0x90 fs/namei.c:5333
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

-> #1 (&opts->dep_lock){+.+.}-{4:4}:
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
tcm_set_name+0x29/0xb0 drivers/usb/gadget/function/f_tcm.c:2669
function_make+0x21c/0x3f0 drivers/usb/gadget/configfs.c:636
configfs_mkdir+0x51e/0xb70 fs/configfs/dir.c:1360
vfs_mkdir+0x361/0x850 fs/namei.c:5276
filename_mkdirat+0x48b/0x5e0 fs/namei.c:5309
__do_sys_mkdir fs/namei.c:5336 [inline]
__se_sys_mkdir fs/namei.c:5333 [inline]
__ia32_sys_mkdir+0x6a/0x90 fs/namei.c:5333
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

-> #0 (gadget_subsys.su_mutex){+.+.}-{4:4}:
check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
uvcg_frame_dw_frame_interval_store+0xdf/0x4b0 drivers/usb/gadget/function/uvc_configfs.c:2076
flush_write_buffer fs/configfs/file.c:207 [inline]
configfs_write_iter+0x302/0x4e0 fs/configfs/file.c:229
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6ac/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e

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
---- ----
rlock(&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.0.2631/16146:
#0: ffff8880211ceb70 (&f->f_pos_lock){+.+.}-{4:4}, at: fdget_pos+0x2aa/0x380 fs/file.c:1259
#1: ffff888022078450 (sb_writers#12){.+.+}-{0:0}, at: ksys_write+0x12a/0x250 fs/read_write.c:739
#2: ffff888075cc2e80 (&buffer->mutex#2){+.+.}-{4:4}, at: configfs_write_iter+0x76/0x4e0 fs/configfs/file.c:226
#3: ffff8880275d5170 (&p->frag_sem){++++}-{4:4}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
#3: ffff8880275d5170 (&p->frag_sem){++++}-{4:4}, at: configfs_write_iter+0x218/0x4e0 fs/configfs/file.c:229

stack backtrace:
CPU: 1 UID: 0 PID: 16146 Comm: syz.0.2631 Tainted: G L syzkaller #0 PREEMPT(full)
Tainted: [L]=SOFTLOCKUP
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_circular_bug.cold+0x178/0x1c7 kernel/locking/lockdep.c:2043
check_noncircular+0x146/0x160 kernel/locking/lockdep.c:2175
check_prev_add+0xeb/0xe60 kernel/locking/lockdep.c:3165
check_prevs_add kernel/locking/lockdep.c:3284 [inline]
validate_chain kernel/locking/lockdep.c:3908 [inline]
__lock_acquire+0x136c/0x1a40 kernel/locking/lockdep.c:5237
lock_acquire kernel/locking/lockdep.c:5868 [inline]
lock_acquire+0x1b9/0x370 kernel/locking/lockdep.c:5825
__mutex_lock_common kernel/locking/mutex.c:646 [inline]
__mutex_lock+0x1a4/0x1bd0 kernel/locking/mutex.c:821
uvcg_frame_dw_frame_interval_store+0xdf/0x4b0 drivers/usb/gadget/function/uvc_configfs.c:2076
flush_write_buffer fs/configfs/file.c:207 [inline]
configfs_write_iter+0x302/0x4e0 fs/configfs/file.c:229
new_sync_write fs/read_write.c:595 [inline]
vfs_write+0x6ac/0x1050 fs/read_write.c:687
ksys_write+0x12a/0x250 fs/read_write.c:739
do_syscall_32_irqs_on arch/x86/entry/syscall_32.c:83 [inline]
__do_fast_syscall_32+0xe7/0x970 arch/x86/entry/syscall_32.c:307
do_fast_syscall_32+0x32/0x70 arch/x86/entry/syscall_32.c:332
entry_SYSENTER_compat_after_hwframe+0x84/0x8e
RIP: 0023:0xf7f93fec
Code: Unable to access opcode bytes at 0xf7f93fc2.
RSP: 002b:00000000f545650c EFLAGS: 00000292 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000004 RCX: 0000000080000080
RDX: 000000000000000b RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
</TASK>


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