general protection fault in do_raw_spin_unlock

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 1d4eb636f0ab Add linux-next specific files for 20180716
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=1186bf0c400000
kernel config: https://syzkaller.appspot.com/x/.config?x=ea5926dddb0db97a
dashboard link: https://syzkaller.appspot.com/bug?extid=83a25334ef203851dc81
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=179ed444400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+83a253...@syzkaller.appspotmail.com

IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
IPVS: ftp: loaded support on port[0] = 21
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
CPU: 1 PID: 24 Comm: kworker/1:1 Not tainted 4.18.0-rc5-next-20180716+ #8
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Workqueue: events p9_poll_workfn
RIP: 0010:debug_spin_unlock kernel/locking/spinlock_debug.c:97 [inline]
RIP: 0010:do_raw_spin_unlock+0x65/0x2f0 kernel/locking/spinlock_debug.c:134
Code: 0a bd 88 48 c7 85 78 ff ff ff b3 8a b5 41 48 c7 45 88 d0 3c 60 81 c7
02 f1 f1 f1 f1 c7 42 04 04 f2 f2 f2 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48
89 f8 65 48 8b 0c 25 28 00 00 00 48 89 4d d0 31 c9
RSP: 0018:ffff8801d945f288 EFLAGS: 00010047
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8770a045
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000004
RBP: ffff8801d945f310 R08: 1ffff1003b28be45 R09: ffffed0035e7bd88
R10: ffffed0035e7bd88 R11: ffff8801af3dec43 R12: 0000000000000000
R13: 1ffff1003b28be51 R14: ffff8801d945f2e8 R15: ffff8801c5811d50
FS: 0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000072c029 CR3: 00000001b19fd000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
__raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:159 [inline]
_raw_spin_unlock_irqrestore+0x27/0xc0 kernel/locking/spinlock.c:184
spin_unlock_irqrestore include/linux/spinlock.h:384 [inline]
p9_conn_cancel+0x9b6/0xd30 net/9p/trans_fd.c:208
p9_poll_mux net/9p/trans_fd.c:620 [inline]
p9_poll_workfn+0x4b2/0x6d0 net/9p/trans_fd.c:1107
process_one_work+0xc73/0x1ba0 kernel/workqueue.c:2153
worker_thread+0x189/0x13c0 kernel/workqueue.c:2296
kthread+0x345/0x410 kernel/kthread.c:246
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:415
Modules linked in:
Dumping ftrace buffer:
(ftrace buffer empty)
---[ end trace 4d86351f63a12683 ]---
RIP: 0010:debug_spin_unlock kernel/locking/spinlock_debug.c:97 [inline]
RIP: 0010:do_raw_spin_unlock+0x65/0x2f0 kernel/locking/spinlock_debug.c:134
Code: 0a bd 88 48 c7 85 78 ff ff ff b3 8a b5 41 48 c7 45 88 d0 3c 60 81 c7
02 f1 f1 f1 f1 c7 42 04 04 f2 f2 f2 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48
89 f8 65 48 8b 0c 25 28 00 00 00 48 89 4d d0 31 c9
RSP: 0018:ffff8801d945f288 EFLAGS: 00010047
RAX: dffffc0000000000 RBX: 0000000000000000 RCX: ffffffff8770a045
RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000004
RBP: ffff8801d945f310 R08: 1ffff1003b28be45 R09: ffffed0035e7bd88
R10: ffffed0035e7bd88 R11: ffff8801af3dec43 R12: 0000000000000000
R13: 1ffff1003b28be51 R14: ffff8801d945f2e8 R15: ffff8801c5811d50
FS: 0000000000000000(0000) GS:ffff8801daf00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 000000000072c029 CR3: 00000001b19fd000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
This bug is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches

[syzbot]

Auto-closing this bug as obsolete.
No recent activity, existing reproducers are no longer triggering the issue.