------------[ cut here ]------------
WARNING: CPU: 0 PID: 0 at net/ipv4/af_inet.c:167 inet_sock_destruct+0x5f6/0x7b0 net/ipv4/af_inet.c:167
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.9.76-g8dec074 #13
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db207cb8 ffffffff81d93169 ffffffff83a47180 ffff8801db207d90
 ffffffff83f2e500 ffffffff832e9cb6 0000000000000009 ffff8801db207d80
 ffffffff8142e371 0000000041b58ab3 ffffffff84189690 ffffffff8142e1b5
Call Trace:
 <IRQ> [   39.079394]  [<ffffffff81d93169>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [   39.079394]  [<ffffffff81d93169>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff8142e371>] panic+0x1bc/0x3a8 kernel/panic.c:179
 [<ffffffff811300f4>] __warn+0x1c4/0x1e0 kernel/panic.c:542
 [<ffffffff8113035c>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff832e9cb6>] inet_sock_destruct+0x5f6/0x7b0 net/ipv4/af_inet.c:167
 [<ffffffff835827e2>] l2tp_tunnel_destruct+0x352/0x5a0 net/l2tp/l2tp_core.c:1329
 [<ffffffff82ee3033>] __sk_destruct+0x53/0x570 net/core/sock.c:1428
 [<ffffffff812920a8>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff812920a8>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff812920a8>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff812920a8>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff812920a8>] rcu_process_callbacks+0x898/0x1300 kernel/rcu/tree.c:3037
 [<ffffffff838b76c6>] __do_softirq+0x206/0x951 kernel/softirq.c:284
 [<ffffffff81145b75>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff81145b75>] irq_exit+0x165/0x190 kernel/softirq.c:405
 [<ffffffff838b62db>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff838b62db>] smp_apic_timer_interrupt+0x7b/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff838b2560>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:735
 <EOI> [   39.158053]  [<ffffffff838af6e6>] ? native_safe_halt+0x6/0x10 arch/x86/include/asm/irqflags.h:53
 [<ffffffff838aed15>] arch_safe_halt arch/x86/include/asm/paravirt.h:103 [inline]
 [<ffffffff838aed15>] default_idle+0x55/0x360 arch/x86/kernel/process.c:295
 [<ffffffff8106bbca>] arch_cpu_idle+0xa/0x10 arch/x86/kernel/process.c:286
 [<ffffffff838afb26>] default_idle_call+0x36/0x60 kernel/sched/idle.c:97
 [<ffffffff812254b0>] cpuidle_idle_call kernel/sched/idle.c:155 [inline]
 [<ffffffff812254b0>] cpu_idle_loop kernel/sched/idle.c:248 [inline]
 [<ffffffff812254b0>] cpu_startup_entry+0x2b0/0x380 kernel/sched/idle.c:303
 [<ffffffff8389c644>] rest_init+0x184/0x190 init/main.c:408
 [<ffffffff84a6f8b6>] start_kernel+0x688/0x6bd init/main.c:663
 [<ffffffff84a6e29d>] x86_64_start_reservations+0x2a/0x2c arch/x86/kernel/head64.c:196
 [<ffffffff84a6e3df>] x86_64_start_kernel+0x140/0x163 arch/x86/kernel/head64.c:177
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..