------------[ cut here ]------------
WARNING: CPU: 1 PID: 3822 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: 1 PID: 3822 Comm: syz-executor781 Not tainted 4.9.123-g8dd3fc2 #27
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db307cc0 ffffffff81eb9689 ffffffff83c48ac0 00000000ffffffff
 0000000000000000 0000000000000001 00000000000000a7 ffff8801db307d80
 ffffffff81423f75 0000000041b58ab3 ffffffff843bb878 ffffffff81423db6
Call Trace:
 <IRQ> [   22.665724]  [<ffffffff81eb9689>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [   22.665724]  [<ffffffff81eb9689>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81423f75>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff81424261>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff811383bc>] warn_slowpath_null+0x2c/0x40 kernel/panic.c:585
 [<ffffffff8342c778>] inet_sock_destruct+0x598/0x760 net/ipv4/af_inet.c:167
 [<ffffffff836c5ab9>] l2tp_tunnel_destruct+0x339/0x590 net/l2tp/l2tp_core.c:1329
 [<ffffffff830280f5>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff81289aae>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff81289aae>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff81289aae>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff81289aae>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff81289aae>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a08880>] __do_softirq+0x210/0x940 kernel/softirq.c:288
 [<ffffffff8114d554>] invoke_softirq kernel/softirq.c:368 [inline]
 [<ffffffff8114d554>] irq_exit+0x114/0x150 kernel/softirq.c:409
 [<ffffffff83a07461>] exiting_irq arch/x86/include/asm/apic.h:669 [inline]
 [<ffffffff83a07461>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:962
 [<ffffffff83a035f0>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [   22.787788]  [<ffffffff83a013bf>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [   22.787788]  [<ffffffff83a013bf>] ? __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 <EOI> [   22.787788]  [<ffffffff83a013bf>] ? _raw_spin_unlock_irqrestore+0x5f/0x70 kernel/locking/spinlock.c:191
 [<ffffffff81222b7b>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff81222b7b>] __wake_up_sync_key+0x4b/0x60 kernel/sched/wait.c:146
 [<ffffffff81592137>] pipe_write+0x967/0xd60 fs/pipe.c:481
 [<ffffffff815734e0>] new_sync_write fs/read_write.c:496 [inline]
 [<ffffffff815734e0>] __vfs_write+0x3e0/0x580 fs/read_write.c:509
 [<ffffffff815772d7>] vfs_write+0x187/0x530 fs/read_write.c:557
 [<ffffffff8157b109>] SYSC_write fs/read_write.c:604 [inline]
 [<ffffffff8157b109>] SyS_write+0xd9/0x1c0 fs/read_write.c:596
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a01c93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..