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WARNING: CPU: 1 PID: 6 at net/xfrm/xfrm_state.c:2139 xfrm_state_fini+0x297/0x330 net/xfrm/xfrm_state.c:2139()
Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 6 Comm: kworker/u4:0 Not tainted 4.4.148-gf057ff9 #81
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
 0000000000000000 0a2f072abdd1482d ffff8801d9a17958 ffffffff81e1448d
 ffffffff83a44e40 ffff8801d9a08000 ffffffff83f26620 0000000000000009
 000000000000085b ffff8801d9a17a18 ffffffff8140ce24 0000000041b58ab3
Call Trace:
 [<ffffffff81e1448d>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81e1448d>] dump_stack+0xc1/0x124 lib/dump_stack.c:51
 [<ffffffff8140ce24>] panic+0x19e/0x38d kernel/panic.c:112
 [<ffffffff8140d048>] warn_slowpath_common.cold.6+0x20/0x20 kernel/panic.c:455
 [<ffffffff81132ac9>] warn_slowpath_null+0x29/0x30 kernel/panic.c:492
 [<ffffffff833f21e7>] xfrm_state_fini+0x297/0x330 net/xfrm/xfrm_state.c:2139
 [<ffffffff833ccd9d>] xfrm_net_exit+0x2d/0x30 net/xfrm/xfrm_policy.c:3038
 [<ffffffff82f643d0>] ops_exit_list.isra.6+0xb0/0x160 net/core/net_namespace.c:134
 [<ffffffff82f67391>] cleanup_net+0x321/0x600 net/core/net_namespace.c:452
 [<ffffffff8118495f>] process_one_work+0x7df/0x1600 kernel/workqueue.c:2064
 [<ffffffff81185859>] worker_thread+0xd9/0xfc0 kernel/workqueue.c:2196
 [<ffffffff81193368>] kthread+0x268/0x300 kernel/kthread.c:211
 [<ffffffff838caad5>] 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..