------------[ cut here ]------------
WARNING: CPU: 1 PID: 2812 at kernel/locking/mutex.c:873 __mutex_trylock_slowpath kernel/locking/mutex.c:873 [inline]
WARNING: CPU: 1 PID: 2812 at kernel/locking/mutex.c:873 mutex_trylock+0x2f9/0x3e0 kernel/locking/mutex.c:908
DEBUG_LOCKS_WARN_ON(in_interrupt())[  572.309295] Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 2812 Comm: syz-executor5 Not tainted 4.9.106-g8b94b87 #43
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db3077f8 ffffffff81eb4209 ffffffff83c48b40 00000000ffffffff
 0000000000000000 0000000000000001 0000000000000369 ffff8801db3078b8
 ffffffff81421de5 0000000041b58ab3 ffffffff843b9990 ffffffff81421c26
Call Trace:
 <IRQ> [  572.362363]  [<ffffffff81eb4209>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [  572.362363]  [<ffffffff81eb4209>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81421de5>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff814220d1>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff81136662>] warn_slowpath_fmt+0xc2/0x100 kernel/panic.c:565
 [<ffffffff839eec09>] __mutex_trylock_slowpath kernel/locking/mutex.c:873 [inline]
 [<ffffffff839eec09>] mutex_trylock+0x2f9/0x3e0 kernel/locking/mutex.c:908
 [<ffffffff81282f59>] exp_funnel_lock kernel/rcu/tree_exp.h:256 [inline]
 [<ffffffff81282f59>] _synchronize_rcu_expedited+0x339/0x840 kernel/rcu/tree_exp.h:569
 [<ffffffff812844b3>] synchronize_rcu_expedited kernel/rcu/tree_exp.h:687 [inline]
 [<ffffffff812844b3>] synchronize_rcu.part.62+0xd3/0x110 kernel/rcu/tree_plugin.h:682
 [<ffffffff81284517>] synchronize_rcu+0x27/0x90 kernel/rcu/tree_plugin.h:685
 [<ffffffff836bccaa>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836bd037>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836bd8f2>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff83021095>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff81287bde>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff81287bde>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff81287bde>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff81287bde>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff81287bde>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a006fb>] __do_softirq+0x20b/0x937 kernel/softirq.c:284
 [<ffffffff8114b227>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff8114b227>] irq_exit+0x147/0x190 kernel/softirq.c:405
 [<ffffffff839ff2e1>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff839ff2e1>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff839fb470>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [  572.643428]  [<ffffffff839f920f>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [  572.643428]  [<ffffffff839f920f>] ? __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 <EOI> [  572.643428]  [<ffffffff839f920f>] ? _raw_spin_unlock_irqrestore+0x5f/0x70 kernel/locking/spinlock.c:191
 [<ffffffff81f1ee5c>] __debug_check_no_obj_freed lib/debugobjects.c:733 [inline]
 [<ffffffff81f1ee5c>] debug_check_no_obj_freed+0x2ec/0x930 lib/debugobjects.c:749
 [<ffffffff81538665>] slab_free_hook mm/slub.c:1348 [inline]
 [<ffffffff81538665>] slab_free_freelist_hook mm/slub.c:1377 [inline]
 [<ffffffff81538665>] slab_free mm/slub.c:2958 [inline]
 [<ffffffff81538665>] kmem_cache_free+0x175/0x310 mm/slub.c:2980
 [<ffffffff814f4436>] anon_vma_free mm/rmap.c:120 [inline]
 [<ffffffff814f4436>] __put_anon_vma+0xe6/0x2c0 mm/rmap.c:1750
 [<ffffffff814f499f>] put_anon_vma include/linux/rmap.h:112 [inline]
 [<ffffffff814f499f>] unlink_anon_vmas+0x38f/0x5b0 mm/rmap.c:413
 [<ffffffff814c4ead>] free_pgtables+0x21d/0x330 mm/memory.c:566
 [<ffffffff814e20f3>] exit_mmap+0x223/0x3f0 mm/mmap.c:2990
 [<ffffffff8112bf83>] __mmput kernel/fork.c:878 [inline]
 [<ffffffff8112bf83>] mmput+0xf3/0x2d0 kernel/fork.c:900
 [<ffffffff81140d66>] exit_mm kernel/exit.c:518 [inline]
 [<ffffffff81140d66>] do_exit+0x906/0x27c0 kernel/exit.c:824
 [<ffffffff81146f41>] do_group_exit+0x111/0x340 kernel/exit.c:941
 [<ffffffff81169d9f>] get_signal+0x4cf/0x1450 kernel/signal.c:2321
 [<ffffffff810524d7>] do_signal+0x87/0x19f0 arch/x86/kernel/signal.c:807
 [<ffffffff81005581>] exit_to_usermode_loop+0xe1/0x120 arch/x86/entry/common.c:157
 [<ffffffff810064d4>] prepare_exit_to_usermode arch/x86/entry/common.c:191 [inline]
 [<ffffffff810064d4>] syscall_return_slowpath arch/x86/entry/common.c:260 [inline]
 [<ffffffff810064d4>] do_syscall_64+0x364/0x490 arch/x86/entry/common.c:287
 [<ffffffff839f9b13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..