===============================
[ INFO: suspicious RCU usage. ]
4.9.116-g52be322 #17 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
2 locks held by udevd/2043:
 #0:  (rcu_read_lock){......}, at: [<ffffffff83027d40>] sock_def_readable+0x0/0x400 include/linux/compiler.h:243
 #1:  (rcu_callback){......}, at: [<ffffffff812878ae>] __rcu_reclaim kernel/rcu/rcu.h:108 [inline]
 #1:  (rcu_callback){......}, at: [<ffffffff812878ae>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 #1:  (rcu_callback){......}, at: [<ffffffff812878ae>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 #1:  (rcu_callback){......}, at: [<ffffffff812878ae>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 #1:  (rcu_callback){......}, at: [<ffffffff812878ae>] rcu_process_callbacks+0x98e/0x12b0 kernel/rcu/tree.c:3037
SELinux: unrecognized netlink message: protocol=0 nlmsg_type=8291 sclass=netlink_route_socket pig=24637 comm=syz-executor2

stack backtrace:
CPU: 1 PID: 2043 Comm: udevd Not tainted 4.9.116-g52be322 #17
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db307d60 ffffffff81eb46a9 ffff8801ccadc800 0000000000000000
 0000000000000002 ffffffff83c6df20 ffff8801b88f08d8 ffff8801db307d90
 ffffffff81426110 ffff8801b88f0780 ffff88019ac5cc48 ffff88019ac5c448
Call Trace:
 <IRQ> [  279.140731]  [<ffffffff81eb46a9>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [  279.140731]  [<ffffffff81eb46a9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81426110>] lockdep_rcu_suspicious.cold.48+0x110/0x141 kernel/locking/lockdep.c:4455
 [<ffffffff81284148>] synchronize_rcu+0x68/0x90 kernel/rcu/tree_plugin.h:675
 [<ffffffff836bed8a>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836bf117>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836bf9d2>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff83022095>] __sk_destruct+0x55/0x590 net/core/sock.c:1428
 [<ffffffff812877ce>] __rcu_reclaim kernel/rcu/rcu.h:118 [inline]
 [<ffffffff812877ce>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
 [<ffffffff812877ce>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
 [<ffffffff812877ce>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
 [<ffffffff812877ce>] rcu_process_callbacks+0x8ae/0x12b0 kernel/rcu/tree.c:3037
 [<ffffffff83a027fb>] __do_softirq+0x20b/0x937 kernel/softirq.c:284
 [<ffffffff8114b277>] invoke_softirq kernel/softirq.c:364 [inline]
 [<ffffffff8114b277>] irq_exit+0x147/0x190 kernel/softirq.c:405
 [<ffffffff83a013e1>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff83a013e1>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff839fd570>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [  279.254579]  [<ffffffff839fb30f>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [  279.254579]  [<ffffffff839fb30f>] ? __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:162 [inline]
 <EOI> [  279.254579]  [<ffffffff839fb30f>] ? _raw_spin_unlock_irqrestore+0x5f/0x70 kernel/locking/spinlock.c:191
 [<ffffffff8122085b>] spin_unlock_irqrestore include/linux/spinlock.h:362 [inline]
 [<ffffffff8122085b>] __wake_up_sync_key+0x4b/0x60 kernel/sched/wait.c:146
 [<ffffffff83027e40>] sock_def_readable+0x100/0x400 net/core/sock.c:2374
 [<ffffffff831c956f>] __netlink_sendskb+0x7f/0xa0 net/netlink/af_netlink.c:1225
 [<ffffffff831d21e6>] netlink_sendskb net/netlink/af_netlink.c:1231 [inline]
 [<ffffffff831d21e6>] netlink_unicast+0x596/0x6f0 net/netlink/af_netlink.c:1319
 [<ffffffff831d2ad5>] netlink_sendmsg+0x795/0xc30 net/netlink/af_netlink.c:1852
 [<ffffffff83017fcc>] sock_sendmsg_nosec net/socket.c:635 [inline]
 [<ffffffff83017fcc>] sock_sendmsg+0xcc/0x110 net/socket.c:645
 [<ffffffff83019a6c>] ___sys_sendmsg+0x6fc/0x840 net/socket.c:1969
 [<ffffffff8301bad9>] __sys_sendmsg+0xd9/0x190 net/socket.c:2003
 [<ffffffff8301bbbd>] SYSC_sendmsg net/socket.c:2014 [inline]
 [<ffffffff8301bbbd>] SyS_sendmsg+0x2d/0x50 net/socket.c:2010
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fbc13>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
ODEBUG: object ffff8801db307ce8 is NOT on stack ffff8801ccb40000, but annotated
------------[ cut here ]------------
WARNING: CPU: 1 PID: 2043 at lib/debugobjects.c:303 debug_object_is_on_stack lib/debugobjects.c:303 [inline]
WARNING: CPU: 1 PID: 2043 at lib/debugobjects.c:303 __debug_object_init.cold.10+0x6b/0x2b0 lib/debugobjects.c:329