------------[ cut here ]------------
WARNING: CPU: 0 PID: 2104 at net/xfrm/xfrm_state.c:2197 xfrm_state_fini+0x2a0/0x340 net/xfrm/xfrm_state.c:2197
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 2104 Comm: kworker/u4:2 Not tainted 4.9.166+ #35
Workqueue: netns cleanup_net
 ffff8801d68cf900 ffffffff81b4ef81 0000000000000000 ffffffff82a39ba0
 00000000ffffffff 0000000000000000 0000000000000009 ffff8801d68cf9e0
 ffffffff813f91aa 0000000041b58ab3 ffffffff82e2ec1a ffffffff813f8fd1
Call Trace:
 [<000000001f3b308d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<000000001f3b308d>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<000000003e7971d3>] panic+0x1d9/0x3bd kernel/panic.c:180
 [<00000000aa290d07>] __warn.cold+0x2f/0x2f kernel/panic.c:546
 [<000000008d2f03ef>] warn_slowpath_null+0x2d/0x40 kernel/panic.c:589
 [<000000009ad6c3cf>] xfrm_state_fini+0x2a0/0x340 net/xfrm/xfrm_state.c:2197
 [<000000001bee132c>] xfrm_net_exit+0x2e/0x40 net/xfrm/xfrm_policy.c:3122
 [<00000000b225c57a>] ops_exit_list.isra.0+0xb0/0x160 net/core/net_namespace.c:136
 [<0000000087d7be6c>] cleanup_net+0x3d6/0x8a0 net/core/net_namespace.c:473
 [<000000004c06eb0c>] process_one_work+0x88b/0x1600 kernel/workqueue.c:2114
 [<0000000067658cbe>] worker_thread+0x5df/0x11d0 kernel/workqueue.c:2251
 [<00000000d59feddd>] kthread+0x278/0x310 kernel/kthread.c:211
 [<000000009b422dce>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373
Kernel Offset: disabled
Rebooting in 86400 seconds..