======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Tainted: G             L     
------------------------------------------------------
syz.9.2961/19799 is trying to acquire lock:
ffffffff8fc13ce8 (gadget_subsys.su_mutex){+.+.}-{4:4}, at: uvcg_streaming_header_allow_link+0x75/0x4d0 drivers/usb/gadget/function/uvc_configfs.c:1750

but task is already holding lock:
ffff8880765cf580 (&sb->s_type->i_mutex_key#26){++++}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
ffff8880765cf580 (&sb->s_type->i_mutex_key#26){++++}-{4:4}, at: configfs_symlink+0x4d0/0x11d0 fs/configfs/symlink.c:201

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&sb->s_type->i_mutex_key#26){++++}-{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:1268
       usbg_make_tpg+0x1e0/0x550 drivers/usb/gadget/function/f_tcm.c:1692
       target_fabric_make_tpg+0xa8/0x6d0 drivers/target/target_core_fabric_configfs.c:947
       configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1369
       vfs_mkdir+0x40c/0x620 fs/namei.c:5410
       filename_mkdirat+0x285/0x510 fs/namei.c:5443
       __do_sys_mkdirat fs/namei.c:5464 [inline]
       __se_sys_mkdirat+0x35/0x150 fs/namei.c:5461
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #2 (tpg_instances_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       tcm_alloc_inst+0x65/0x1a0 drivers/usb/gadget/function/f_tcm.c:2687
       try_get_usb_function_instance drivers/usb/gadget/functions.c:28 [inline]
       usb_get_function_instance+0xe3/0x2f0 drivers/usb/gadget/functions.c:44
       function_make+0x127/0x360 drivers/usb/gadget/configfs.c:626
       configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1369
       vfs_mkdir+0x40c/0x620 fs/namei.c:5410
       filename_mkdirat+0x285/0x510 fs/namei.c:5443
       __do_sys_mkdirat fs/namei.c:5464 [inline]
       __se_sys_mkdirat+0x35/0x150 fs/namei.c:5461
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #1 (func_lock){+.+.}-{4:4}:
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       try_get_usb_function_instance drivers/usb/gadget/functions.c:18 [inline]
       usb_get_function_instance+0x2e/0x2f0 drivers/usb/gadget/functions.c:44
       function_make+0x127/0x360 drivers/usb/gadget/configfs.c:626
       configfs_mkdir+0x4f6/0x9e0 fs/configfs/dir.c:1369
       vfs_mkdir+0x40c/0x620 fs/namei.c:5410
       filename_mkdirat+0x285/0x510 fs/namei.c:5443
       __do_sys_mkdirat fs/namei.c:5464 [inline]
       __se_sys_mkdirat+0x35/0x150 fs/namei.c:5461
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

-> #0 (gadget_subsys.su_mutex){+.+.}-{4:4}:
       check_prev_add kernel/locking/lockdep.c:3209 [inline]
       check_prevs_add kernel/locking/lockdep.c:3328 [inline]
       validate_chain kernel/locking/lockdep.c:3952 [inline]
       __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
       lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
       __mutex_lock_common kernel/locking/mutex.c:646 [inline]
       __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
       uvcg_streaming_header_allow_link+0x75/0x4d0 drivers/usb/gadget/function/uvc_configfs.c:1750
       configfs_symlink+0x74e/0x11d0 fs/configfs/symlink.c:211
       vfs_symlink+0x18b/0x330 fs/namei.c:5794
       filename_symlinkat+0x1cd/0x410 fs/namei.c:5819
       __do_sys_symlinkat fs/namei.c:5839 [inline]
       __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5834
       do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
       do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
       entry_SYSCALL_64_after_hwframe+0x77/0x7f

other info that might help us debug this:

Chain exists of:
  gadget_subsys.su_mutex --> tpg_instances_lock --> &sb->s_type->i_mutex_key#26

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#26);
                               lock(tpg_instances_lock);
                               lock(&sb->s_type->i_mutex_key#26);
  lock(gadget_subsys.su_mutex);

 *** DEADLOCK ***

locks held by syz.9.2961/19799: 2, last CPU#1:
 #0: ffff88801d72c460 (sb_writers#19){.+.+}-{0:0}, at: mnt_want_write+0x41/0x90 fs/namespace.c:494
 #1: ffff8880765cf580 (&sb->s_type->i_mutex_key#26){++++}-{4:4}, at: inode_lock include/linux/fs.h:1024 [inline]
 #1: ffff8880765cf580 (&sb->s_type->i_mutex_key#26){++++}-{4:4}, at: configfs_symlink+0x4d0/0x11d0 fs/configfs/symlink.c:201

stack backtrace:
CPU: 1 UID: 0 PID: 19799 Comm: syz.9.2961 Tainted: G             L      syzkaller #0 PREEMPT(full) 
Tainted: [L]=SOFTLOCKUP
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/05/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0xe8/0x150 lib/dump_stack.c:120
 print_circular_bug+0x2e2/0x300 kernel/locking/lockdep.c:2087
 check_noncircular+0x12f/0x150 kernel/locking/lockdep.c:2219
 check_prev_add kernel/locking/lockdep.c:3209 [inline]
 check_prevs_add kernel/locking/lockdep.c:3328 [inline]
 validate_chain kernel/locking/lockdep.c:3952 [inline]
 __lock_acquire+0x164c/0x2de0 kernel/locking/lockdep.c:5288
 lock_acquire+0x115/0x350 kernel/locking/lockdep.c:5942
 __mutex_lock_common kernel/locking/mutex.c:646 [inline]
 __mutex_lock+0x19d/0x1550 kernel/locking/mutex.c:821
 uvcg_streaming_header_allow_link+0x75/0x4d0 drivers/usb/gadget/function/uvc_configfs.c:1750
 configfs_symlink+0x74e/0x11d0 fs/configfs/symlink.c:211
 vfs_symlink+0x18b/0x330 fs/namei.c:5794
 filename_symlinkat+0x1cd/0x410 fs/namei.c:5819
 __do_sys_symlinkat fs/namei.c:5839 [inline]
 __se_sys_symlinkat+0x4e/0x2b0 fs/namei.c:5834
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x166/0x520 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f152479e159
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:00007f1525606028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f1524a26090 RCX: 00007f152479e159
RDX: 0000200000001600 RSI: ffffffffffffff9c RDI: 0000200000001500
RBP: 00007f152483506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f1524a26128 R14: 00007f1524a26090 R15: 00007fff87dc3838
 </TASK>