------------[ cut here ]------------
WARNING: CPU: 0 PID: 4761 at net/xfrm/xfrm_state.c:2175 xfrm_state_fini+0x2a0/0x340 net/xfrm/xfrm_state.c:2175
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4761 Comm: kworker/u4:6 Not tainted 4.9.121-g681e57b #25
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
 ffff8801d4da7950 ffffffff81eb7e29 ffffffff83c48ac0 00000000ffffffff
 0000000000000000 0000000000000000 000000000000087f ffff8801d4da7a10
 ffffffff81423b05 0000000041b58ab3 ffffffff843bb838 ffffffff81423946
Call Trace:
 [<ffffffff81eb7e29>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb7e29>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81423b05>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff81423df1>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff81137f4c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff8351dd80>] xfrm_state_fini+0x2a0/0x340 net/xfrm/xfrm_state.c:2175
 [<ffffffff834fad2d>] xfrm_net_exit+0x2d/0x30 net/xfrm/xfrm_policy.c:3066
 [<ffffffff8305ee20>] ops_exit_list.isra.6+0xb0/0x160 net/core/net_namespace.c:136
 [<ffffffff83061cf1>] cleanup_net+0x321/0x630 net/core/net_namespace.c:473
 [<ffffffff8118eff1>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118fde6>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119ef5d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839ffe9c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..