===============================
[ INFO: suspicious RCU usage. ]
4.9.122-g54068d6 #26 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
4 locks held by syz-executor6/3875:
 #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff8113334b>] dup_mmap kernel/fork.c:574 [inline]
 #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff8113334b>] dup_mm kernel/fork.c:1156 [inline]
 #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff8113334b>] copy_mm kernel/fork.c:1210 [inline]
 #0:  (&mm->mmap_sem){++++++}, at: [<ffffffff8113334b>] copy_process.part.51+0x39db/0x6330 kernel/fork.c:1678
 #1:  (&mm->mmap_sem/1){+.+.+.}, at: [<ffffffff81133371>] dup_mmap kernel/fork.c:583 [inline]
 #1:  (&mm->mmap_sem/1){+.+.+.}, at: [<ffffffff81133371>] dup_mm kernel/fork.c:1156 [inline]
 #1:  (&mm->mmap_sem/1){+.+.+.}, at: [<ffffffff81133371>] copy_mm kernel/fork.c:1210 [inline]
 #1:  (&mm->mmap_sem/1){+.+.+.}, at: [<ffffffff81133371>] copy_process.part.51+0x3a01/0x6330 kernel/fork.c:1678
 #2:  (rcu_read_lock){......}, at: [<ffffffff81cfbbb0>] INIT_LIST_HEAD include/linux/list.h:28 [inline]
 #2:  (rcu_read_lock){......}, at: [<ffffffff81cfbbb0>] avc_compute_av+0xb0/0x610 security/selinux/avc.c:975
 #3:  (rcu_callback){......}, at: [<ffffffff81289b4e>] __rcu_reclaim kernel/rcu/rcu.h:108 [inline]
 #3:  (rcu_callback){......}, at: [<ffffffff81289b4e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 #3:  (rcu_callback){......}, at: [<ffffffff81289b4e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 #3:  (rcu_callback){......}, at: [<ffffffff81289b4e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 #3:  (rcu_callback){......}, at: [<ffffffff81289b4e>] rcu_process_callbacks+0x98e/0x12b0 kernel/rcu/tree.c:3037

stack backtrace:
CPU: 1 PID: 3875 Comm: syz-executor6 Not tainted 4.9.122-g54068d6 #26
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db307d60 ffffffff81eb8829 ffff8801b5e58000 0000000000000000
 0000000000000002 ffffffff83c6e380 ffff8801d5086dd8 ffff8801db307d90
 ffffffff814285d1 ffff8801d5086c80 ffff88019f925d48 ffff88019f925548
Call Trace:
 <IRQ> [ 1014.959529]  [<ffffffff81eb8829>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [ 1014.959529]  [<ffffffff81eb8829>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff814285d1>] lockdep_rcu_suspicious.cold.48+0x110/0x141 kernel/locking/lockdep.c:4455
 [<ffffffff812863e8>] synchronize_rcu+0x68/0x90 kernel/rcu/tree_plugin.h:675
 [<ffffffff836c3e3a>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836c41c7>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836c4a82>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff830270f5>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff81289a6e>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff81289a6e>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff81289a6e>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff81289a6e>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff81289a6e>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a078c0>] __do_softirq+0x210/0x940 kernel/softirq.c:288
 [<ffffffff8114d514>] invoke_softirq kernel/softirq.c:368 [inline]
 [<ffffffff8114d514>] irq_exit+0x114/0x150 kernel/softirq.c:409
 [<ffffffff83a064a1>] exiting_irq arch/x86/include/asm/apic.h:669 [inline]
 [<ffffffff83a064a1>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:962
 [<ffffffff83a02630>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [ 1015.074244]  [<ffffffff83a003cf>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [ 1015.074244]  [<ffffffff83a003cf>] ? __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 <EOI> [ 1015.074244]  [<ffffffff83a003cf>] ? _raw_spin_unlock_irqrestore+0x5f/0x70 kernel/locking/spinlock.c:191
 [<ffffffff81cfb029>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff81cfb029>] avc_reclaim_node security/selinux/avc.c:543 [inline]
 [<ffffffff81cfb029>] avc_alloc_node+0x289/0x3d0 security/selinux/avc.c:561
 [<ffffffff81cfbc78>] avc_insert security/selinux/avc.c:672 [inline]
 [<ffffffff81cfbc78>] avc_compute_av+0x178/0x610 security/selinux/avc.c:978
 [<ffffffff81cfd8b9>] avc_has_perm_noaudit+0x319/0x450 security/selinux/avc.c:1114
 [<ffffffff81d0c4ca>] cred_has_capability+0x13a/0x2e0 security/selinux/hooks.c:1666
 [<ffffffff81d0c6be>] selinux_vm_enough_memory+0x4e/0x60 security/selinux/hooks.c:2255
 [<ffffffff81cf29d7>] security_vm_enough_memory_mm+0x77/0xb0 security/security.c:232
 [<ffffffff8113383f>] dup_mmap kernel/fork.c:615 [inline]
 [<ffffffff8113383f>] dup_mm kernel/fork.c:1156 [inline]
 [<ffffffff8113383f>] copy_mm kernel/fork.c:1210 [inline]
 [<ffffffff8113383f>] copy_process.part.51+0x3ecf/0x6330 kernel/fork.c:1678
 [<ffffffff81136120>] copy_process kernel/fork.c:1503 [inline]
 [<ffffffff81136120>] _do_fork+0x1b0/0xdd0 kernel/fork.c:1963
 [<ffffffff81136e17>] SYSC_clone kernel/fork.c:2075 [inline]
 [<ffffffff81136e17>] SyS_clone+0x37/0x50 kernel/fork.c:2069
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff83a00cd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
ODEBUG: object ffff8801db307ce8 is NOT on stack ffff8801a03c8000, but annotated
------------[ cut here ]------------
WARNING: CPU: 1 PID: 3875 at lib/debugobjects.c:303 debug_object_is_on_stack lib/debugobjects.c:303 [inline]
WARNING: CPU: 1 PID: 3875 at lib/debugobjects.c:303 __debug_object_init.cold.10+0x6b/0x2b0 lib/debugobjects.c:329