===============================
[ INFO: suspicious RCU usage. ]
4.9.110-g00a0bcb #7 Not tainted
-------------------------------
kernel/rcu/tree_plugin.h:678 Illegal synchronize_rcu() in RCU read-side critical section!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
3 locks held by syz-executor2/3843:
 #0:  (tasklist_lock){.+.+..}, at: [<ffffffff81146622>] do_wait+0x392/0x950 kernel/exit.c:1562
 #1:  (rcu_read_lock){......}, at: [<ffffffff81cf5320>] INIT_LIST_HEAD include/linux/list.h:28 [inline]
 #1:  (rcu_read_lock){......}, at: [<ffffffff81cf5320>] avc_compute_av+0xb0/0x610 security/selinux/avc.c:975
 #2:  (rcu_callback){......}, at: [<ffffffff8128777e>] __rcu_reclaim kernel/rcu/rcu.h:108 [inline]
 #2:  (rcu_callback){......}, at: [<ffffffff8128777e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 #2:  (rcu_callback){......}, at: [<ffffffff8128777e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 #2:  (rcu_callback){......}, at: [<ffffffff8128777e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 #2:  (rcu_callback){......}, at: [<ffffffff8128777e>] rcu_process_callbacks+0x98e/0x12b0 kernel/rcu/tree.c:3037

stack backtrace:
CPU: 1 PID: 3843 Comm: syz-executor2 Not tainted 4.9.110-g00a0bcb #7
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db307d60 ffffffff81eb2329 ffff8801ba6c1800 0000000000000000
 0000000000000002 ffffffff83c6df00 ffff8801d30428d8 ffff8801db307d90
 ffffffff81425fc0 ffff8801d3042780 ffff8801a7ecbb48 ffff8801a7ecb348
Call Trace:
 <IRQ> [  237.321579]  [<ffffffff81eb2329>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [  237.321579]  [<ffffffff81eb2329>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81425fc0>] lockdep_rcu_suspicious.cold.48+0x110/0x141 kernel/locking/lockdep.c:4455
 [<ffffffff81284018>] synchronize_rcu+0x68/0x90 kernel/rcu/tree_plugin.h:675
 [<ffffffff836baeda>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836bb267>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836bbb22>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff8301f095>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff8128769e>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff8128769e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff8128769e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff8128769e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff8128769e>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff839fe8bb>] __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
 [<ffffffff839fd4a1>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff839fd4a1>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff839f9630>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [  237.434991]  [<ffffffff839f73ef>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [  237.434991]  [<ffffffff839f73ef>] ? __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 <EOI> [  237.434991]  [<ffffffff839f73ef>] ? _raw_spin_unlock_irqrestore+0x5f/0x70 kernel/locking/spinlock.c:191
 [<ffffffff81cf4799>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff81cf4799>] avc_reclaim_node security/selinux/avc.c:543 [inline]
 [<ffffffff81cf4799>] avc_alloc_node+0x289/0x3d0 security/selinux/avc.c:561
 [<ffffffff81cf53e8>] avc_insert security/selinux/avc.c:672 [inline]
 [<ffffffff81cf53e8>] avc_compute_av+0x178/0x610 security/selinux/avc.c:978
 [<ffffffff81cf74c4>] avc_has_perm_noaudit security/selinux/avc.c:1114 [inline]
 [<ffffffff81cf74c4>] avc_has_perm+0x364/0x4f0 security/selinux/avc.c:1148
 [<ffffffff81d096bc>] task_has_perm+0x1fc/0x330 security/selinux/hooks.c:1615
 [<ffffffff81d09813>] selinux_task_wait+0x23/0x30 security/selinux/hooks.c:3954
 [<ffffffff81cf0553>] security_task_wait+0x73/0xb0 security/security.c:1032
 [<ffffffff81142f01>] wait_consider_task+0x2a1/0x3630 kernel/exit.c:1381
 [<ffffffff811466b3>] do_wait_thread kernel/exit.c:1494 [inline]
 [<ffffffff811466b3>] do_wait+0x423/0x950 kernel/exit.c:1565
 [<ffffffff811475eb>] SYSC_wait4 kernel/exit.c:1697 [inline]
 [<ffffffff811475eb>] SyS_wait4+0x12b/0x1f0 kernel/exit.c:1662
 [<ffffffff812fd447>] C_SYSC_wait4+0x237/0x280 kernel/compat.c:543
 [<ffffffff812fd80c>] compat_SyS_wait4+0x2c/0x40 kernel/compat.c:536
 [<ffffffff8111ac05>] sys32_waitpid+0x25/0x30 arch/x86/ia32/sys_ia32.c:172
 [<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
 [<ffffffff839f93d0>] entry_SYSENTER_compat+0x90/0xa2 arch/x86/entry/entry_64_compat.S:137
ODEBUG: object ffff8801db307ce8 is NOT on stack ffff8801aa900000, but annotated
------------[ cut here ]------------
WARNING: CPU: 1 PID: 3843 at lib/debugobjects.c:303 debug_object_is_on_stack lib/debugobjects.c:303 [inline]
WARNING: CPU: 1 PID: 3843 at lib/debugobjects.c:303 __debug_object_init.cold.10+0x6b/0x2b0 lib/debugobjects.c:329