======================================================
WARNING: possible circular locking dependency detected
syzkaller #0 Not tainted
------------------------------------------------------
syz.6.517/6756 is trying to acquire lock:
ffffffff8d7b02b0 (gadget_subsys.su_mutex){+.+.}-{3:3}, at: uvcg_streaming_header_allow_link+0x6d/0x4a0 drivers/usb/gadget/function/uvc_configfs.c:884

but task is already holding lock:
ffff8880553d2ee0 (&sb->s_type->i_mutex_key#34){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:764 [inline]
ffff8880553d2ee0 (&sb->s_type->i_mutex_key#34){+.+.}-{3:3}, at: configfs_symlink+0x47b/0x13c0 fs/configfs/symlink.c:192

which lock already depends on the new lock.


the existing dependency chain (in reverse order) is:

-> #3 (&sb->s_type->i_mutex_key#34){+.+.}-{3:3}:
       down_write+0x36/0x60 kernel/locking/rwsem.c:1573
       inode_lock include/linux/fs.h:764 [inline]
       configfs_depend_item_unlocked+0x14f/0x430 fs/configfs/dir.c:1255
       usbg_make_tpg+0x1dd/0x550 drivers/usb/gadget/function/f_tcm.c:1371
       target_fabric_make_tpg+0xa0/0x6d0 drivers/target/target_core_fabric_configfs.c:913
       configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x386/0x570 fs/namei.c:4157
       do_mkdirat+0x1d8/0x440 fs/namei.c:4182
       __do_sys_mkdir fs/namei.c:4202 [inline]
       __se_sys_mkdir fs/namei.c:4200 [inline]
       __x64_sys_mkdir+0x6a/0x80 fs/namei.c:4200
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #2 (tpg_instances_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
       tcm_alloc_inst+0x61/0x190 drivers/usb/gadget/function/f_tcm.c:2366
       try_get_usb_function_instance drivers/usb/gadget/functions.c:28 [inline]
       usb_get_function_instance+0xd9/0x2e0 drivers/usb/gadget/functions.c:44
       function_make+0x118/0x350 drivers/usb/gadget/configfs.c:615
       configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x386/0x570 fs/namei.c:4157
       do_mkdirat+0x1d8/0x440 fs/namei.c:4182
       __do_sys_mkdir fs/namei.c:4202 [inline]
       __se_sys_mkdir fs/namei.c:4200 [inline]
       __x64_sys_mkdir+0x6a/0x80 fs/namei.c:4200
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
       entry_SYSCALL_64_after_hwframe+0x68/0xd2

-> #1 (func_lock){+.+.}-{3:3}:
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
       try_get_usb_function_instance drivers/usb/gadget/functions.c:18 [inline]
       usb_get_function_instance+0x2a/0x2e0 drivers/usb/gadget/functions.c:44
       function_make+0x118/0x350 drivers/usb/gadget/configfs.c:615
       configfs_mkdir+0x511/0x9e0 fs/configfs/dir.c:1360
       vfs_mkdir+0x386/0x570 fs/namei.c:4157
       do_mkdirat+0x1d8/0x440 fs/namei.c:4182
       __do_sys_mkdir fs/namei.c:4202 [inline]
       __se_sys_mkdir fs/namei.c:4200 [inline]
       __x64_sys_mkdir+0x6a/0x80 fs/namei.c:4200
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 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:3095 [inline]
       check_prevs_add kernel/locking/lockdep.c:3214 [inline]
       validate_chain kernel/locking/lockdep.c:3830 [inline]
       __lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063
       lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5678
       __mutex_lock_common kernel/locking/mutex.c:603 [inline]
       __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
       uvcg_streaming_header_allow_link+0x6d/0x4a0 drivers/usb/gadget/function/uvc_configfs.c:884
       configfs_symlink+0x5a4/0x13c0 fs/configfs/symlink.c:202
       vfs_symlink+0x245/0x3d0 fs/namei.c:4522
       do_symlinkat+0x1b6/0x400 fs/namei.c:4551
       __do_sys_symlinkat fs/namei.c:4568 [inline]
       __se_sys_symlinkat fs/namei.c:4565 [inline]
       __x64_sys_symlinkat+0x95/0xa0 fs/namei.c:4565
       do_syscall_x64 arch/x86/entry/common.c:46 [inline]
       do_syscall_64+0x4c/0xa0 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 --> tpg_instances_lock --> &sb->s_type->i_mutex_key#34

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&sb->s_type->i_mutex_key#34);
                               lock(tpg_instances_lock);
                               lock(&sb->s_type->i_mutex_key#34);
  lock(gadget_subsys.su_mutex);

 *** DEADLOCK ***

2 locks held by syz.6.517/6756:
 #0: ffff888143ab0460 (sb_writers#25){.+.+}-{0:0}, at: mnt_want_write+0x3d/0x90 fs/namespace.c:402
 #1: ffff8880553d2ee0 (&sb->s_type->i_mutex_key#34){+.+.}-{3:3}, at: inode_lock include/linux/fs.h:764 [inline]
 #1: ffff8880553d2ee0 (&sb->s_type->i_mutex_key#34){+.+.}-{3:3}, at: configfs_symlink+0x47b/0x13c0 fs/configfs/symlink.c:192

stack backtrace:
CPU: 0 PID: 6756 Comm: syz.6.517 Not tainted syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
Call Trace:
 <TASK>
 dump_stack_lvl+0x188/0x24e lib/dump_stack.c:106
 check_noncircular+0x296/0x330 kernel/locking/lockdep.c:2170
 check_prev_add kernel/locking/lockdep.c:3095 [inline]
 check_prevs_add kernel/locking/lockdep.c:3214 [inline]
 validate_chain kernel/locking/lockdep.c:3830 [inline]
 __lock_acquire+0x2d18/0x7c40 kernel/locking/lockdep.c:5063
 lock_acquire+0x1bb/0x4a0 kernel/locking/lockdep.c:5678
 __mutex_lock_common kernel/locking/mutex.c:603 [inline]
 __mutex_lock+0x12d/0xae0 kernel/locking/mutex.c:747
 uvcg_streaming_header_allow_link+0x6d/0x4a0 drivers/usb/gadget/function/uvc_configfs.c:884
 configfs_symlink+0x5a4/0x13c0 fs/configfs/symlink.c:202
 vfs_symlink+0x245/0x3d0 fs/namei.c:4522
 do_symlinkat+0x1b6/0x400 fs/namei.c:4551
 __do_sys_symlinkat fs/namei.c:4568 [inline]
 __se_sys_symlinkat fs/namei.c:4565 [inline]
 __x64_sys_symlinkat+0x95/0xa0 fs/namei.c:4565
 do_syscall_x64 arch/x86/entry/common.c:46 [inline]
 do_syscall_64+0x4c/0xa0 arch/x86/entry/common.c:76
 entry_SYSCALL_64_after_hwframe+0x68/0xd2
RIP: 0033:0x7f812299e159
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:00007f81237dd028 EFLAGS: 00000246 ORIG_RAX: 000000000000010a
RAX: ffffffffffffffda RBX: 00007f8122c25fa0 RCX: 00007f812299e159
RDX: 0000200000001600 RSI: ffffffffffffff9c RDI: 0000200000001500
RBP: 00007f8122a3506b R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007f8122c26038 R14: 00007f8122c25fa0 R15: 00007ffcf6c32af8
 </TASK>