=====================================
WARNING: bad unlock balance detected!
4.14.218-syzkaller #0 Not tainted
-------------------------------------
syz-executor.3/25169 is trying to release lock (sb_writers) at:
[<ffffffff87043f5f>] ovl_workdir_create.cold+0xeb/0xf7 syzkaller/managers/linux-4-14/kernel/fs/overlayfs/super.c:546
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz-executor.3/25169:
 #0:  (&type->s_umount_key#64/1){+.+.}, at: [<ffffffff818705e6>] alloc_super syzkaller/managers/linux-4-14/kernel/fs/super.c:251 [inline]
 #0:  (&type->s_umount_key#64/1){+.+.}, at: [<ffffffff818705e6>] sget_userns+0x556/0xc10 syzkaller/managers/linux-4-14/kernel/fs/super.c:516

stack backtrace:
CPU: 1 PID: 25169 Comm: syz-executor.3 Not tainted 4.14.218-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack syzkaller/managers/linux-4-14/kernel/lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 syzkaller/managers/linux-4-14/kernel/lib/dump_stack.c:58
 print_unlock_imbalance_bug syzkaller/managers/linux-4-14/kernel/./include/trace/events/lock.h:58 [inline]
 __lock_release syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:3769 [inline]
 lock_release.cold+0x70/0xbf syzkaller/managers/linux-4-14/kernel/kernel/locking/lockdep.c:4017
 ovl_workdir_create.cold+0xeb/0xf7 syzkaller/managers/linux-4-14/kernel/fs/overlayfs/super.c:546
 ovl_fill_super+0xfe9/0x2610 syzkaller/managers/linux-4-14/kernel/fs/overlayfs/super.c:988
 mount_nodev+0x4c/0xf0 syzkaller/managers/linux-4-14/kernel/fs/super.c:1180
 mount_fs+0x92/0x2a0 syzkaller/managers/linux-4-14/kernel/fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 syzkaller/managers/linux-4-14/kernel/fs/namespace.c:1046
 vfs_kern_mount syzkaller/managers/linux-4-14/kernel/fs/namespace.c:1036 [inline]
 do_new_mount syzkaller/managers/linux-4-14/kernel/fs/namespace.c:2549 [inline]
 do_mount+0xe53/0x2a00 syzkaller/managers/linux-4-14/kernel/fs/namespace.c:2879
 SYSC_mount syzkaller/managers/linux-4-14/kernel/fs/namespace.c:3095 [inline]
 SyS_mount+0xa8/0x120 syzkaller/managers/linux-4-14/kernel/fs/namespace.c:3072
 do_syscall_64+0x1d5/0x640 syzkaller/managers/linux-4-14/kernel/arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x465b09
RSP: 002b:00007fce684dd188 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 000000000056bf60 RCX: 0000000000465b09
RDX: 00000000200000c0 RSI: 0000000020000000 RDI: 000000000040000d
RBP: 00000000004b069f R08: 0000000020000100 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 000000000056bf60
R13: 00007fff33e86f0f R14: 00007fce684dd300 R15: 0000000000022000
overlayfs: failed to create directory ./file1\/work (errno: 30); mounting read-only
------------[ cut here ]------------
WARNING: CPU: 1 PID: 7998 at fs/namespace.c:1178 cleanup_mnt+0x222/0x2c0 syzkaller/managers/linux-4-14/kernel/fs/namespace.c:1178