======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.7.5238/19208 is trying to acquire lock:
ffff8881678bd900 (&sb->s_type->i_mutex_key#24){++++}-{4:4}, at: configfs_depend_item_unlocked+0x153/0x420

but task is already holding lock:
ffff88811129f518 (&opts->dep_lock){+.+.}-{4:4}, at: usbg_make_tpg+0x147/0x590

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #2 (&opts->dep_lock){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       tcm_set_name+0x2b/0xd0
       function_make+0x1a8/0x360
       configfs_mkdir+0x4f6/0x9e0
       vfs_mkdir+0x406/0x620
       filename_mkdirat+0x285/0x510
       __se_sys_mkdirat+0x35/0x150
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (gadget_subsys.su_mutex){+.+.}-{4:4}:
       __mutex_lock+0x19d/0x1550
       uvcg_streaming_header_allow_link+0x75/0x4d0
       configfs_symlink+0x59a/0x1030
       vfs_symlink+0x18b/0x330
       filename_symlinkat+0x1cd/0x410
       __se_sys_symlinkat+0x4e/0x2b0
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (&sb->s_type->i_mutex_key#24){++++}-{4:4}:
       __lock_acquire+0x1520/0x2cf0
       lock_acquire+0x106/0x350
       down_write+0x96/0x200
       configfs_depend_item_unlocked+0x153/0x420
       usbg_make_tpg+0x1f6/0x590
       target_fabric_make_tpg+0xa8/0x6d0
       configfs_mkdir+0x4f6/0x9e0
       vfs_mkdir+0x406/0x620
       filename_mkdirat+0x285/0x510
       __se_sys_mkdirat+0x35/0x150
       do_syscall_64+0x174/0x580
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  &sb->s_type->i_mutex_key#24 --> gadget_subsys.su_mutex --> &opts->dep_lock

 Possible unsafe locking scenario:

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

 *** DEADLOCK ***

5 locks held by syz.7.5238/19208:
 #0: ffff888168e36450 (sb_writers#13){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90
 #1: ffff888112f83580 (&sb->s_type->i_mutex_key#8/1){+.+.}-{4:4}, at: filename_create+0x200/0x370
 #2: ffffffff8f71b0c8 (&subsys->su_mutex){+.+.}-{4:4}, at: configfs_mkdir+0x4b0/0x9e0
 #3: ffffffff8fa4e980 (tpg_instances_lock){+.+.}-{4:4}, at: usbg_make_tpg+0xf7/0x590
 #4: ffff88811129f518 (&opts->dep_lock){+.+.}-{4:4}, at: usbg_make_tpg+0x147/0x590

stack backtrace:
CPU: 1 UID: 0 PID: 19208 Comm: syz.7.5238 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.2-debian-1.16.2-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150
 print_circular_bug+0x2e1/0x300
 check_noncircular+0x12e/0x150
 __lock_acquire+0x1520/0x2cf0
 lock_acquire+0x106/0x350
 down_write+0x96/0x200
 configfs_depend_item_unlocked+0x153/0x420
 usbg_make_tpg+0x1f6/0x590
 target_fabric_make_tpg+0xa8/0x6d0
 configfs_mkdir+0x4f6/0x9e0
 vfs_mkdir+0x406/0x620
 filename_mkdirat+0x285/0x510
 __se_sys_mkdirat+0x35/0x150
 do_syscall_64+0x174/0x580
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f127039e019
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:00007f127121c028 EFLAGS: 00000246 ORIG_RAX: 0000000000000102
RAX: ffffffffffffffda RBX: 00007f1270625fa0 RCX: 00007f127039e019
RDX: 00000000000001ff RSI: 0000200000001000 RDI: ffffffffffffff9c
RBP: 00007f127043500c R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1270626038 R14: 00007f1270625fa0 R15: 00007ffe4d18e048
 </TASK>
