------------[ cut here ]------------
WARNING: CPU: 1 PID: 3765 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: 3765 Comm: syz-executor468 Not tainted 4.9.123-g8dd3fc2 #31
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> [   31.529172]  [<ffffffff81eb9689>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [   31.529172]  [<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> [   31.651101]  [<ffffffff81281910>] ? rcu_momentary_dyntick_idle+0x1e0/0x1e0 kernel/rcu/tree.c:330
 [<ffffffff81451c55>] trace_mm_page_free include/trace/events/kmem.h:150 [inline]
 [<ffffffff81451c55>] free_pages_prepare mm/page_alloc.c:1032 [inline]
 [<ffffffff81451c55>] free_pcp_prepare mm/page_alloc.c:1087 [inline]
 [<ffffffff81451c55>] free_hot_cold_page+0x685/0x840 mm/page_alloc.c:2473
 [<ffffffff81452239>] free_hot_cold_page_list+0x99/0x340 mm/page_alloc.c:2521
 [<ffffffff814681da>] release_pages+0x60a/0x970 mm/swap.c:794
 [<ffffffff8150c497>] free_pages_and_swap_cache+0x117/0x160 mm/swap_state.c:273
 [<ffffffff814c2774>] tlb_flush_mmu_free+0xb4/0x150 mm/memory.c:259
 [<ffffffff814c6149>] tlb_flush_mmu mm/memory.c:268 [inline]
 [<ffffffff814c6149>] tlb_finish_mmu+0x29/0xd0 mm/memory.c:279
 [<ffffffff814e4cd4>] exit_mmap+0x234/0x3f0 mm/mmap.c:3023
 [<ffffffff8112db63>] __mmput kernel/fork.c:884 [inline]
 [<ffffffff8112db63>] mmput+0xf3/0x2d0 kernel/fork.c:906
 [<ffffffff81143096>] exit_mm kernel/exit.c:514 [inline]
 [<ffffffff81143096>] do_exit+0x906/0x27b0 kernel/exit.c:820
 [<ffffffff81149251>] do_group_exit+0x111/0x340 kernel/exit.c:937
 [<ffffffff8114949d>] SYSC_exit_group kernel/exit.c:948 [inline]
 [<ffffffff8114949d>] SyS_exit_group+0x1d/0x20 kernel/exit.c:946
 [<ffffffff81006da7>] do_syscall_32_irqs_on arch/x86/entry/common.c:325 [inline]
 [<ffffffff81006da7>] do_fast_syscall_32+0x2f7/0x870 arch/x86/entry/common.c:387
 [<ffffffff83a03390>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..