WARNING in __mutex_unlock_slowpath

[syzbot <syzbot+35666cba7f0a337e2e79@syzkaller.appspotmail.com>]

Hello,

syzbot hit the following crash on upstream commit
bf8f5de17442bba5f811e7e724980730e079ee11 (Sat Apr 28 17:05:04 2018 +0000)
MAINTAINERS: add myself as maintainer of AFFS
syzbot dashboard link:  
https://syzkaller.appspot.com/bug?extid=35666cba7f0a337e2e79

C reproducer: https://syzkaller.appspot.com/x/repro.c?id=5686569910403072
syzkaller reproducer:  
https://syzkaller.appspot.com/x/repro.syz?id=5767017265102848
Raw console output:  
https://syzkaller.appspot.com/x/log.txt?id=6346308495343616
Kernel config:  
https://syzkaller.appspot.com/x/.config?id=7043958930931867332
compiler: gcc (GCC) 8.0.1 20180413 (experimental)

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Reported-by: syzbot+35666cba7f0a337e2e79@syzkaller.appspotmail.com
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------------[ cut here ]------------
DEBUG_LOCKS_WARN_ON(__owner_task(owner) != current)
WARNING: CPU: 0 PID: 4525 at kernel/locking/mutex.c:1032  
__mutex_unlock_slowpath+0x62e/0x8a0 kernel/locking/mutex.c:1032
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4525 Comm: syz-executor809 Not tainted 4.17.0-rc2+ #22
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+0x1b9/0x294 lib/dump_stack.c:113
  panic+0x22f/0x4de kernel/panic.c:184
  __warn.cold.8+0x163/0x1b3 kernel/panic.c:536
  report_bug+0x252/0x2d0 lib/bug.c:186
  fixup_bug arch/x86/kernel/traps.c:178 [inline]
  do_error_trap+0x1de/0x490 arch/x86/kernel/traps.c:296
  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
  invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:__mutex_unlock_slowpath+0x62e/0x8a0 kernel/locking/mutex.c:1032
RSP: 0018:ffff8801cf31f138 EFLAGS: 00010286
RAX: 0000000000000033 RBX: 1ffff10039e63e30 RCX: ffffffff8160b82d
RDX: 0000000000000000 RSI: ffffffff816104e1 RDI: 0000000000000001
RBP: ffff8801cf31f2a8 R08: ffff8801d9042180 R09: fffffbfff11b0974
R10: fffffbfff11b0974 R11: ffffffff88d84ba3 R12: ffffffff8a713a20
R13: dffffc0000000000 R14: 0000000000000000 R15: ffff8801989d6b08
  mutex_unlock+0xd/0x10 kernel/locking/mutex.c:614
  kvm_hv_eventfd_deassign arch/x86/kvm/hyperv.c:1434 [inline]
  kvm_vm_ioctl_hv_eventfd+0x1ea/0x24b arch/x86/kvm/hyperv.c:1451
  kvm_arch_vm_ioctl+0x155e/0x2690 arch/x86/kvm/x86.c:4563
  kvm_vm_ioctl+0x246/0x1d90 arch/x86/kvm/../../../virt/kvm/kvm_main.c:3100
  vfs_ioctl fs/ioctl.c:46 [inline]
  file_ioctl fs/ioctl.c:500 [inline]
  do_vfs_ioctl+0x1cf/0x16a0 fs/ioctl.c:684
  ksys_ioctl+0xa9/0xd0 fs/ioctl.c:701
  __do_sys_ioctl fs/ioctl.c:708 [inline]
  __se_sys_ioctl fs/ioctl.c:706 [inline]
  __x64_sys_ioctl+0x73/0xb0 fs/ioctl.c:706
  do_syscall_64+0x1b1/0x800 arch/x86/entry/common.c:287
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4401f9
RSP: 002b:00007ffcd5727a48 EFLAGS: 00000217 ORIG_RAX: 0000000000000010
RAX: ffffffffffffffda RBX: 6d766b2f7665642f RCX: 00000000004401f9
RDX: 0000000020000140 RSI: 000000004018aebd RDI: 00000000000000ee
RBP: 00000000006ca018 R08: 00000000004002c8 R09: 00000000004002c8
R10: 00000000004002c8 R11: 0000000000000217 R12: 0000000000401720
R13: 00000000004017b0 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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