WARNING in xfrm_state_fini (2)

Hello,

syzbot hit the following crash on upstream commit
4bf772b14675411a69b3c807f73006de0fe4b649 (Fri Feb 2 01:48:47 2018 +0000)
Merge tag 'drm-for-v4.16' of git://people.freedesktop.org/~airlied/linux

Unfortunately, I don't have any reproducer for this crash yet.
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+0bf0519d6e0de15914fe@syzkaller.appspotmail.com
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netlink: 3 bytes leftover after parsing attributes in process  
`syz-executor2'.
WARNING: CPU: 0 PID: 28 at net/xfrm/xfrm_state.c:2341  
xfrm_state_fini+0x46a/0x620 net/xfrm/xfrm_state.c:2341
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 28 Comm: kworker/u4:2 Not tainted 4.15.0+ #202
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: netns cleanup_net
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:1097
RIP: 0010:xfrm_state_fini+0x46a/0x620 net/xfrm/xfrm_state.c:2341
RSP: 0000:ffff8801d993f148 EFLAGS: 00010293
RAX: ffff8801d9926000 RBX: ffff8801b899a100 RCX: ffffffff84be327a
RDX: 0000000000000000 RSI: 0000000000000000 RDI: ffffffff86ac93f8
RBP: ffff8801d993f2a0 R08: 1ffff1003b327dbc R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 1ffff1003b327e2b
R13: ffff8801d993f278 R14: 1ffff1003b327e2f R15: ffff8801b899b500
  xfrm_net_exit+0x25/0x70 net/xfrm/xfrm_policy.c:2978
  ops_exit_list.isra.6+0xae/0x150 net/core/net_namespace.c:142
  cleanup_net+0x6a3/0xcc0 net/core/net_namespace.c:517
  process_one_work+0xbbf/0x1af0 kernel/workqueue.c:2113
  worker_thread+0x223/0x1990 kernel/workqueue.c:2247
  kthread+0x33c/0x400 kernel/kthread.c:238
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:542
Dumping ftrace buffer:
    (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


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