WARNING: bad unlock balance in ovl_workdir_create (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: a35d65bedfbc Linux 4.14.267
git tree: linux-4.14.y
console output: https://syzkaller.appspot.com/x/log.txt?x=1430a812700000
kernel config: https://syzkaller.appspot.com/x/.config?x=8535d773e783c59a
dashboard link: https://syzkaller.appspot.com/bug?extid=48617d87ee45a631eb2e
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+48617d...@syzkaller.appspotmail.com

overlayfs: failed to create directory ./file1/work (errno: 30); mounting read-only
=====================================
hfsplus: unable to find HFS+ superblock
WARNING: bad unlock balance detected!
4.14.267-syzkaller #0 Not tainted
-------------------------------------
syz-executor.3/9970 is trying to release lock (sb_writers) at:
[<ffffffff87078294>] 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.3/9970:
#0: (&type->s_umount_key#50/1){+.+.}, at: [<ffffffff81876656>] alloc_super fs/super.c:251 [inline]
#0: (&type->s_umount_key#50/1){+.+.}, at: [<ffffffff81876656>] sget_userns+0x556/0xc10 fs/super.c:516

stack backtrace:
CPU: 1 PID: 9970 Comm: syz-executor.3 Not tainted 4.14.267-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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
ovl_fill_super+0xfe9/0x2610 fs/overlayfs/super.c:988
mount_nodev+0x4c/0xf0 fs/super.c:1180
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+0xe65/0x2a10 fs/namespace.c:2902
SYSC_mount fs/namespace.c:3118 [inline]
SyS_mount+0xa8/0x120 fs/namespace.c:3095
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb
RIP: 0033:0x7fbe23744059
RSP: 002b:00007fbe220b9168 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 00007fbe23856f60 RCX: 00007fbe23744059
RDX: 0000000020000080 RSI: 0000000020000040 RDI: 0000000000000000
RBP: 00007fbe2379e08d R08: 0000000020000340 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffcf26438af R14: 00007fbe220b9300 R15: 0000000000022000
------------[ cut here ]------------
WARNING: CPU: 0 PID: 7979 at fs/namespace.c:1178 cleanup_mnt+0x222/0x2c0 fs/namespace.c:1178


---
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[syzbot]

syzbot has found a reproducer for the following issue on:

HEAD commit: a35d65bedfbc Linux 4.14.267
git tree: linux-4.14.y

console output: https://syzkaller.appspot.com/x/log.txt?x=13e9ed86700000

kernel config: https://syzkaller.appspot.com/x/.config?x=8535d773e783c59a
dashboard link: https://syzkaller.appspot.com/bug?extid=48617d87ee45a631eb2e
compiler: gcc version 10.2.1 20210110 (Debian 10.2.1-6)

syz repro: https://syzkaller.appspot.com/x/repro.syz?x=12d7dbbc700000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=16fe016a700000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+48617d...@syzkaller.appspotmail.com

overlayfs: failed to create directory ./file1/work (errno: 30); mounting read-only
=====================================

WARNING: bad unlock balance detected!
4.14.267-syzkaller #0 Not tainted
-------------------------------------

syz-executor341/7962 is trying to release lock (sb_writers) at:

[<ffffffff87078294>] 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-executor341/7962:
#0: (&type->s_umount_key#46/1){+.+.}, at: [<ffffffff81876656>] alloc_super fs/super.c:251 [inline]
#0: (&type->s_umount_key#46/1){+.+.}, at: [<ffffffff81876656>] sget_userns+0x556/0xc10 fs/super.c:516

stack backtrace:
CPU: 1 PID: 7962 Comm: syz-executor341 Not tainted 4.14.267-syzkaller #0

Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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
ovl_fill_super+0xfe9/0x2610 fs/overlayfs/super.c:988
mount_nodev+0x4c/0xf0 fs/super.c:1180
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+0xe65/0x2a10 fs/namespace.c:2902
SYSC_mount fs/namespace.c:3118 [inline]
SyS_mount+0xa8/0x120 fs/namespace.c:3095
do_syscall_64+0x1d5/0x640 arch/x86/entry/common.c:292
entry_SYSCALL_64_after_hwframe+0x46/0xbb

RIP: 0033:0x7f3488b390e9
RSP: 002b:00007fff2f0687d8 EFLAGS: 00000246 ORIG_RAX: 00000000000000a5
RAX: ffffffffffffffda RBX: 0030656c69662f2e RCX: 00007f3488b390e9

RDX: 0000000020000080 RSI: 0000000020000040 RDI: 0000000000000000

RBP: 00007f3488afd0d0 R08: 0000000020000340 R09: 0000000000000000
R10: 0000000000000000 R11