Hello,

syzbot hit the following crash on upstream commit
1f07476ec143bbed7bf0b641749783b1094b4c4f (Tue Jan 23 20:45:40 2018 +0000)
Merge tag 'pci-v4.15-fixes-3' of  
git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci

So far this crash happened 3 times on upstream.
C reproducer is attached.
syzkaller reproducer is attached.
Raw console output is attached.
compiler: gcc (GCC) 7.1.1 20170620
.config is attached.
user-space arch: i386

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Reported-by: syzbot+eb17c6162478cc50632c@syzkaller.appspotmail.com
It will help syzbot understand when the bug is fixed. See footer for  
details.
If you forward the report, please keep this part and the footer.

WARNING: CPU: 0 PID: 5568 at drivers/vhost/vhost.c:646  
vhost_dev_cleanup+0x1074/0x1690 drivers/vhost/vhost.c:646
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 5568 Comm: syzkaller070365 Not tainted 4.15.0-rc9+ #187
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+0x194/0x257 lib/dump_stack.c:53
  panic+0x1e4/0x41c kernel/panic.c:183
  __warn+0x1dc/0x200 kernel/panic.c:547
  report_bug+0x211/0x2d0 lib/bug.c:184
  fixup_bug.part.11+0x37/0x80 arch/x86/kernel/traps.c:178
  fixup_bug arch/x86/kernel/traps.c:247 [inline]
  do_error_trap+0x2d7/0x3e0 arch/x86/kernel/traps.c:296
  do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:315
  invalid_op+0x22/0x40 arch/x86/entry/entry_64.S:1096
RIP: 0010:vhost_dev_cleanup+0x1074/0x1690 drivers/vhost/vhost.c:646
RSP: 0018:ffff8801d93af160 EFLAGS: 00010293
RAX: ffff8801d9238600 RBX: ffff8801b0ec6ac0 RCX: ffffffff84132694
RDX: 0000000000000000 RSI: 0000000000000001 RDI: ffff8801b0ec6b68
RBP: ffff8801d93af2a0 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1003b275e37
R13: ffff8801b0ec6d58 R14: ffff8801b0ec6b80 R15: ffff8801b0ec6bd0
  vhost_net_release+0x78/0x190 drivers/vhost/net.c:999
  __fput+0x327/0x7e0 fs/file_table.c:210
  ____fput+0x15/0x20 fs/file_table.c:244
  task_work_run+0x199/0x270 kernel/task_work.c:113
  exit_task_work include/linux/task_work.h:22 [inline]
  do_exit+0x9bb/0x1ad0 kernel/exit.c:865
  do_group_exit+0x149/0x400 kernel/exit.c:968
  get_signal+0x73f/0x16c0 kernel/signal.c:2335
  do_signal+0x90/0x1eb0 arch/x86/kernel/signal.c:809
  exit_to_usermode_loop+0x214/0x310 arch/x86/entry/common.c:158
  prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
  syscall_return_slowpath arch/x86/entry/common.c:264 [inline]
  do_syscall_32_irqs_on arch/x86/entry/common.c:333 [inline]
  do_fast_syscall_32+0xbfd/0xf9d arch/x86/entry/common.c:389
  entry_SYSENTER_compat+0x54/0x63 arch/x86/entry/entry_64_compat.S:129
RIP: 0023:0xf7f12c79
RSP: 002b:00000000f7f0e12c EFLAGS: 00000292 ORIG_RAX: 00000000000000f0
RAX: fffffffffffffe00 RBX: 00000000080fe004 RCX: 0000000000000000
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 00000000080fe004
RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
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