------------[ cut here ]------------
WARNING: CPU: 0 PID: 3 at net/ipv4/af_inet.c:167 inet_sock_destruct+0x598/0x760 net/ipv4/af_inet.c:167
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 3 Comm: ksoftirqd/0 Not tainted 4.9.122-g54068d6 #30
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801d99efa48 ffffffff81eb8829 ffffffff83c48ac0 00000000ffffffff
 0000000000000000 0000000000000000 00000000000000a7 ffff8801d99efb08
 ffffffff81423f35 0000000041b58ab3 ffffffff843bb838 ffffffff81423d76
Call Trace:
 [<ffffffff81eb8829>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb8829>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81423f35>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff81424221>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff8113837c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff8342b758>] inet_sock_destruct+0x598/0x760 net/ipv4/af_inet.c:167
 [<ffffffff836c4ac9>] l2tp_tunnel_destruct+0x339/0x590 net/l2tp/l2tp_core.c:1329
 [<ffffffff830270f5>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff81289a6e>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff81289a6e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff81289a6e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff81289a6e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff81289a6e>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a078c0>] __do_softirq+0x210/0x940 kernel/softirq.c:288
 [<ffffffff8114d2e0>] run_ksoftirqd+0x30/0x60 kernel/softirq.c:680
 [<ffffffff811aa569>] smpboot_thread_fn+0x5c9/0x900 kernel/smpboot.c:163
 [<ffffffff8119f38d>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff83a00e9c>] 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..