------------[ cut here ]------------
WARNING: CPU: 0 PID: 6648 at net/xfrm/xfrm_policy.c:2976 xfrm_policy_fini+0x280/0x310 net/xfrm/xfrm_policy.c:2976()
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 6648 Comm: kworker/u4:4 Not tainted 4.4.147-ga5fc665 #80
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
 0000000000000000 bd62ba0c9a78b010 ffff8800a2fdf940 ffffffff81e12a4d
 ffffffff83a44d40 ffff8800a2d3e000 ffffffff83f25c20 0000000000000009
 0000000000000ba0 ffff8800a2fdfa00 ffffffff8140c6a4 0000000041b58ab3
Call Trace:
 [<ffffffff81e12a4d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e12a4d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8140c6a4>] panic+0x19e/0x38d kernel/panic.c:112
 [<ffffffff8140c8c8>] warn_slowpath_common.cold.6+0x20/0x20 kernel/panic.c:455
 [<ffffffff81132349>] warn_slowpath_null+0x29/0x30 kernel/panic.c:492
 [<ffffffff833cb2a0>] xfrm_policy_fini+0x280/0x310 net/xfrm/xfrm_policy.c:2976
 [<ffffffff833cb355>] xfrm_net_exit+0x25/0x30 net/xfrm/xfrm_policy.c:3037
 [<ffffffff82f62990>] ops_exit_list.isra.6+0xb0/0x160 net/core/net_namespace.c:134
 [<ffffffff82f65951>] cleanup_net+0x321/0x600 net/core/net_namespace.c:452
 [<ffffffff811841df>] process_one_work+0x7df/0x1600 kernel/workqueue.c:2064
 [<ffffffff811850d9>] worker_thread+0xd9/0xfc0 kernel/workqueue.c:2196
 [<ffffffff81192be8>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838c9095>] ret_from_fork+0x55/0x80 arch/x86/entry/entry_64.S:510
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..