NILFS error (device loop3): nilfs_readdir: zero-length directory entry
Remounting filesystem read-only
overlayfs: failed to create directory ./file1/work (errno: 30); mounting read-only
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
=====================================
WARNING: bad unlock balance detected!
4.14.306-syzkaller #0 Not tainted
-------------------------------------
syz-executor.3/9731 is trying to release lock (sb_writers) at:
[<ffffffff87084c9d>] ovl_workdir_create.cold+0xeb/0xf7 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.3/9731:
 #0:  (&type->s_umount_key#48/1){+.+.}, at: [<ffffffff81879206>] alloc_super fs/super.c:251 [inline]
 #0:  (&type->s_umount_key#48/1){+.+.}, at: [<ffffffff81879206>] sget_userns+0x556/0xc10 fs/super.c:516

stack backtrace:
CPU: 0 PID: 9731 Comm: syz-executor.3 Not tainted 4.14.306-syzkaller #0
NILFS (loop1): broken superblock, retrying with spare superblock (blocksize = 1024)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/16/2023
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x1b2/0x281 lib/dump_stack.c:58
 print_unlock_imbalance_bug include/trace/events/lock.h:58 [inline]
 __lock_release kernel/locking/lockdep.c:3769 [inline]
 lock_release.cold+0x70/0xbf kernel/locking/lockdep.c:4017
 ovl_workdir_create.cold+0xeb/0xf7 fs/overlayfs/super.c:546
overlayfs: fs on './file0' does not support file handles, falling back to index=off.
 ovl_fill_super+0xfe9/0x2610 fs/overlayfs/super.c:988
overlayfs: upper fs does not support tmpfile.
overlayfs: upper fs does not support xattr.
 mount_nodev+0x4c/0xf0 fs/super.c:1180
NILFS error (device loop2): nilfs_readdir: zero-length directory entry
 mount_fs+0x92/0x2a0 fs/super.c:1237
 vfs_kern_mount.part.0+0x5b/0x470 fs/namespace.c:1046
 vfs_kern_mount fs/namespace.c:1036 [inline]
 do_new_mount fs/namespace.c:2572 [inline]
 do_mount+0xe65/0x2a30 fs/namespace.c:2905
Remounting filesystem read-only
 SYSC_mount fs/namespace.c:3121 [inline]
 SyS_mount+0xa8/0x120 fs/namespace.c:3098
NILFS (loop1): mounting unchecked fs
 do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
 entry_SYSCALL_64_after_hwframe+0x5e/0xd3
NILFS (loop1): recovery complete
RIP: 0033:0x7fdb7b08f0f9
RSP: 002b:00007fdb79601168 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fdb7b1aef80 RCX: 00007fdb7b08f0f9
RDX: 00000000200002c0 RSI: 0000000020000040 RDI: 0000000000000000
F2FS-fs (loop0): Found nat_bits in checkpoint
RBP: 00007fdb7b0eaae9 R08: 0000000020000080 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffd219f3eef R14: 00007fdb79601300 R15: 0000000000022000
overlayfs: upper fs does not support tmpfile.
NILFS (loop1): segctord starting. Construction interval = 5 seconds, CP frequency < 30 seconds
overlayfs: upper fs does not support xattr.
NILFS error (device loop5): nilfs_readdir: zero-length directory entry
Remounting filesystem read-only
------------[ cut here ]------------
WARNING: CPU: 0 PID: 8008 at fs/namespace.c:1178 cleanup_mnt+0x222/0x2c0 fs/namespace.c:1178