------------[ cut here ]------------
WARNING: CPU: 1 PID: 17739 at kernel/locking/mutex.c:873 __mutex_trylock_slowpath kernel/locking/mutex.c:873 [inline]
WARNING: CPU: 1 PID: 17739 at kernel/locking/mutex.c:873 mutex_trylock+0x2f9/0x3e0 kernel/locking/mutex.c:908
DEBUG_LOCKS_WARN_ON(in_interrupt())[  561.862154] Kernel panic - not syncing: panic_on_warn set ...

CPU: 1 PID: 17739 Comm: syz-executor7 Not tainted 4.9.118-g47b77b8 #72
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db307830 ffffffff81eb4b89 ffffffff83c48980 00000000ffffffff
 0000000000000000 0000000000000001 0000000000000369 ffff8801db3078f0
 ffffffff81421c25 0000000041b58ab3 ffffffff843bbfe8 ffffffff81421a66
Call Trace:
 <IRQ> [  561.915150]  [<ffffffff81eb4b89>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [  561.915150]  [<ffffffff81eb4b89>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81421c25>] panic+0x1bf/0x3bc kernel/panic.c:179
 [<ffffffff81421f11>] __warn.cold.9+0xc1/0x17f kernel/panic.c:542
 [<ffffffff811366d2>] warn_slowpath_fmt+0xc2/0x100 kernel/panic.c:565
 [<ffffffff839f1ba9>] __mutex_trylock_slowpath kernel/locking/mutex.c:873 [inline]
 [<ffffffff839f1ba9>] mutex_trylock+0x2f9/0x3e0 kernel/locking/mutex.c:908
 [<ffffffff81282b29>] exp_funnel_lock kernel/rcu/tree_exp.h:256 [inline]
 [<ffffffff81282b29>] _synchronize_rcu_expedited+0x339/0x840 kernel/rcu/tree_exp.h:569
 [<ffffffff81284083>] synchronize_rcu_expedited kernel/rcu/tree_exp.h:687 [inline]
 [<ffffffff81284083>] synchronize_rcu.part.62+0xd3/0x110 kernel/rcu/tree_plugin.h:682
 [<ffffffff812840e7>] synchronize_rcu+0x27/0x90 kernel/rcu/tree_plugin.h:685
 [<ffffffff836bfc1a>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836bffa7>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836c0862>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff830230f5>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff812877ae>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff812877ae>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff812877ae>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff812877ae>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff812877ae>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a0367b>] __do_softirq+0x20b/0x937 kernel/softirq.c:284
 [<ffffffff839fda9c>] do_softirq_own_stack+0x1c/0x30 arch/x86/entry/entry_64.S:843
 <EOI> [  562.159655]  [<ffffffff81149859>] do_softirq.part.14+0x99/0xb0 kernel/softirq.c:328
 [<ffffffff81149936>] do_softirq arch/x86/include/asm/preempt.h:22 [inline]
 [<ffffffff81149936>] __local_bh_enable_ip+0xc6/0xd0 kernel/softirq.c:181
 [<ffffffff836ca936>] local_bh_enable include/linux/bottom_half.h:31 [inline]
 [<ffffffff836ca936>] pppol2tp_sendmsg+0x4f6/0x790 net/l2tp/l2tp_ppp.c:340
 [<ffffffff83018fcc>] sock_sendmsg_nosec net/socket.c:636 [inline]
 [<ffffffff83018fcc>] sock_sendmsg+0xcc/0x110 net/socket.c:646
 [<ffffffff8301a7ea>] ___sys_sendmsg+0x47a/0x840 net/socket.c:1970
 [<ffffffff8301cd41>] __sys_sendmmsg+0x161/0x3d0 net/socket.c:2060
 [<ffffffff8301cfe5>] SYSC_sendmmsg net/socket.c:2091 [inline]
 [<ffffffff8301cfe5>] SyS_sendmmsg+0x35/0x60 net/socket.c:2086
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fca93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
Dumping ftrace buffer:
   (ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..