WARNING: bad unlock balance in ucma_destroy_id

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    5b394b2ddf03 Linux 4.19-rc1
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=117e0da6400000
kernel config:  https://syzkaller.appspot.com/x/.config?x=49927b422dcf0b29
dashboard link: https://syzkaller.appspot.com/bug?extid=4b628fcc748474003457
compiler:       gcc (GCC) 8.0.1 20180413 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=13351e2e400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+4b628fcc748474003457@xxxxxxxxxxxxxxxxxxxxxxxxx

IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready
8021q: adding VLAN 0 to HW filter on device team0

=====================================
WARNING: bad unlock balance detected!
4.19.0-rc1+ #211 Not tainted
-------------------------------------
syz-executor0/6666 is trying to release lock (&file->mut) at:
[<ffffffff84c3796b>] ucma_destroy_id+0x2cb/0x550  
drivers/infiniband/core/ucma.c:624
but there are no more locks to release!

other info that might help us debug this:
1 lock held by syz-executor0/6666:
 #0: 00000000faad4ebe (&file->mut){+.+.}, at: ucma_destroy_id+0x26b/0x550  
drivers/infiniband/core/ucma.c:622

stack backtrace:
CPU: 0 PID: 6666 Comm: syz-executor0 Not tainted 4.19.0-rc1+ #211
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x1c9/0x2b4 lib/dump_stack.c:113
 print_unlock_imbalance_bug.cold.49+0xcc/0xd8 kernel/locking/lockdep.c:3465
 __lock_release kernel/locking/lockdep.c:3672 [inline]
 lock_release+0x76e/0x9f0 kernel/locking/lockdep.c:3920
 __mutex_unlock_slowpath+0x102/0x8c0 kernel/locking/mutex.c:1198
 mutex_unlock+0xd/0x10 kernel/locking/mutex.c:713
 ucma_destroy_id+0x2cb/0x550 drivers/infiniband/core/ucma.c:624
 ucma_write+0x336/0x420 drivers/infiniband/core/ucma.c:1680
 __vfs_write+0x117/0x9d0 fs/read_write.c:485
 vfs_write+0x1fc/0x560 fs/read_write.c:549
 ksys_write+0x101/0x260 fs/read_write.c:598
 __do_sys_write fs/read_write.c:610 [inline]
 __se_sys_write fs/read_write.c:607 [inline]
 __x64_sys_write+0x73/0xb0 fs/read_write.c:607
 do_syscall_64+0x1b9/0x820 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x457089
Code: fd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 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 0f 83 cb b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f3d32b48c78 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 00007f3d32b496d4 RCX: 0000000000457089
RDX: 0000000000000018 RSI: 0000000020000480 RDI: 0000000000000005
RBP: 0000000000930140 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 00000000ffffffff
R13: 00000000004d7470 R14: 00000000004c17a8 R15: 0000000000000001


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