======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.1.1020/10273 is trying to acquire lock:
ffffffff8ddf6c50 (gadget_subsys.su_mutex){+.+.}-{3:3}, at: uvcg_frame_dw_max_video_frame_buffer_size_store+0x115/0x370 drivers/usb/gadget/function/uvc_configfs.c:2023

but task is already holding lock:
ffff88802ba0f778 (&p->frag_sem){++++}-{3:3}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
ffff88802ba0f778 (&p->frag_sem){++++}-{3:3}, at: configfs_write_iter+0x215/0x400 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+0xa7/0x230 kernel/locking/rwsem.c:1584
       configfs_rmdir+0x3e4/0x980 fs/configfs/dir.c:1534
       vfs_rmdir+0x352/0x4b0 fs/namei.c:4251
       do_rmdir+0x29f/0x590 fs/namei.c:4310
       __do_sys_unlinkat fs/namei.c:4488 [inline]
       __se_sys_unlinkat fs/namei.c:4482 [inline]
       __x64_sys_unlinkat+0xc4/0xe0 fs/namei.c:4482
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #2 (&sb->s_type->i_mutex_key#23){++++}-{3:3}:
       down_write+0x97/0x200 kernel/locking/rwsem.c:1573
       inode_lock include/linux/fs.h:804 [inline]
       configfs_depend_item_unlocked+0x157/0x430 fs/configfs/dir.c:1255
       usbg_make_tpg+0x1f7/0x580 drivers/usb/gadget/function/f_tcm.c:1341
       target_fabric_make_tpg+0xa4/0x6d0 drivers/target/target_core_fabric_configfs.c:939
       configfs_mkdir+0x515/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x2a5/0x470 fs/namei.c:4168
       do_mkdirat+0x1dc/0x450 fs/namei.c:4191
       __do_sys_mkdir fs/namei.c:4211 [inline]
       __se_sys_mkdir fs/namei.c:4209 [inline]
       __x64_sys_mkdir+0x6e/0x80 fs/namei.c:4209
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (&opts->dep_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
       tcm_set_name+0x2a/0x90 drivers/usb/gadget/function/f_tcm.c:2317
       function_make+0x199/0x350 drivers/usb/gadget/configfs.c:635
       configfs_mkdir+0x515/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x2a5/0x470 fs/namei.c:4168
       do_mkdirat+0x1dc/0x450 fs/namei.c:4191
       __do_sys_mkdir fs/namei.c:4211 [inline]
       __se_sys_mkdir fs/namei.c:4209 [inline]
       __x64_sys_mkdir+0x6e/0x80 fs/namei.c:4209
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #0 (gadget_subsys.su_mutex){+.+.}-{3:3}:
       check_prev_add kernel/locking/lockdep.c:3134 [inline]
       check_prevs_add kernel/locking/lockdep.c:3253 [inline]
       validate_chain kernel/locking/lockdep.c:3869 [inline]
       __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
       lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
       uvcg_frame_dw_max_video_frame_buffer_size_store+0x115/0x370 drivers/usb/gadget/function/uvc_configfs.c:2023
       flush_write_buffer fs/configfs/file.c:207 [inline]
       configfs_write_iter+0x312/0x400 fs/configfs/file.c:229
       call_write_iter include/linux/fs.h:2018 [inline]
       new_sync_write fs/read_write.c:491 [inline]
       vfs_write+0x474/0x9a0 fs/read_write.c:584
       ksys_write+0x151/0x260 fs/read_write.c:637
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

other info that might help us debug this:

Chain exists of:
  gadget_subsys.su_mutex --> &sb->s_type->i_mutex_key#23 --> &p->frag_sem

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  rlock(&p->frag_sem);
                               lock(&sb->s_type->i_mutex_key#23);
                               lock(&p->frag_sem);
  lock(gadget_subsys.su_mutex);

 *** DEADLOCK ***

4 locks held by syz.1.1020/10273:
 #0: ffff88802b60a0c8 (&f->f_pos_lock){+.+.}-{3:3}, at: __fdget_pos+0x2a3/0x330 fs/file.c:1040
 #1: ffff888141ede418 (sb_writers#16){.+.+}-{0:0}, at: vfs_write+0x21e/0x9a0 fs/read_write.c:580
 #2: ffff88802f31da88 (&buffer->mutex){+.+.}-{3:3}, at: configfs_write_iter+0x81/0x400 fs/configfs/file.c:226
 #3: ffff88802ba0f778 (&p->frag_sem){++++}-{3:3}, at: flush_write_buffer fs/configfs/file.c:205 [inline]
 #3: ffff88802ba0f778 (&p->frag_sem){++++}-{3:3}, at: configfs_write_iter+0x215/0x400 fs/configfs/file.c:229

stack backtrace:
CPU: 1 PID: 10273 Comm: syz.1.1020 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x18c/0x250 lib/dump_stack.c:106
 check_noncircular+0x2fc/0x400 kernel/locking/lockdep.c:2187
 check_prev_add kernel/locking/lockdep.c:3134 [inline]
 check_prevs_add kernel/locking/lockdep.c:3253 [inline]
 validate_chain kernel/locking/lockdep.c:3869 [inline]
 __lock_acquire+0x37ef/0x7d80 kernel/locking/lockdep.c:5137
 lock_acquire+0x19e/0x420 kernel/locking/lockdep.c:5754
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x135/0xc80 kernel/locking/mutex.c:747
 uvcg_frame_dw_max_video_frame_buffer_size_store+0x115/0x370 drivers/usb/gadget/function/uvc_configfs.c:2023
 flush_write_buffer fs/configfs/file.c:207 [inline]
 configfs_write_iter+0x312/0x400 fs/configfs/file.c:229
 call_write_iter include/linux/fs.h:2018 [inline]
 new_sync_write fs/read_write.c:491 [inline]
 vfs_write+0x474/0x9a0 fs/read_write.c:584
 ksys_write+0x151/0x260 fs/read_write.c:637
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7faa33b9e0d9
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:00007faa34b0e028 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007faa33e25fa0 RCX: 00007faa33b9e0d9
RDX: 0000000000000004 RSI: 00002000000006c0 RDI: 0000000000000007
RBP: 00007faa33c35024 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007faa33e26038 R14: 00007faa33e25fa0 R15: 00007ffe251d15b8
 </TASK>