------------[ cut here ]------------
WARNING: CPU: 0 PID: 4636 at net/xfrm/xfrm_policy.c:3057 xfrm_policy_fini+0x26f/0x2f0 net/xfrm/xfrm_policy.c:3057
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4636 Comm: kworker/u4:7 Not tainted 4.9.135+ #116
Workqueue: netns cleanup_net
 ffff8801a8d07928 ffffffff81b42b89 ffffffff82a38ba0 00000000ffffffff
 0000000000000000 0000000000000000 0000000000000bf1 ffff8801a8d079e8
 ffffffff813f6aa5 0000000041b58ab3 ffffffff82e2b1c3 ffffffff813f68e6
Call Trace:
 [<ffffffff81b42b89>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81b42b89>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff813f6aa5>] panic+0x1bf/0x39f kernel/panic.c:179
 [<ffffffff813f6d74>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff810dbe2c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff8263907f>] xfrm_policy_fini+0x26f/0x2f0 net/xfrm/xfrm_policy.c:3057
 [<ffffffff82639125>] xfrm_net_exit+0x25/0x30 net/xfrm/xfrm_policy.c:3118
 [<ffffffff822e3a10>] ops_exit_list.isra.0+0xb0/0x160 net/core/net_namespace.c:136
 [<ffffffff822e6772>] cleanup_net+0x3f2/0x8b0 net/core/net_namespace.c:473
 [<ffffffff81130d61>] process_one_work+0x831/0x1530 kernel/workqueue.c:2092
 [<ffffffff81131b36>] worker_thread+0xd6/0x1140 kernel/workqueue.c:2226
 [<ffffffff811428dd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff82816d5c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Kernel Offset: disabled
Rebooting in 86400 seconds..