===============================
[ INFO: suspicious RCU usage. ]
4.9.119-g9dc978d #23 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: [<ffffffff815c174a>] dput.part.29+0x2a/0x7b0 fs/dcache.c:790
 #1:  (rcu_callback[  350.764889] netlink: 24 bytes leftover after parsing attributes in process `syz-executor5'.
){......}, at: [<ffffffff812878ae>] __rcu_reclaim kernel/rcu/rcu.h:108 [inline]
){......}, at: [<ffffffff812878ae>] rcu_do_batch kernel/rcu/tree.c:2789 [inline]
){......}, at: [<ffffffff812878ae>] invoke_rcu_callbacks kernel/rcu/tree.c:3053 [inline]
){......}, at: [<ffffffff812878ae>] __rcu_process_callbacks kernel/rcu/tree.c:3020 [inline]
){......}, at: [<ffffffff812878ae>] rcu_process_callbacks+0x98e/0x12b0 kernel/rcu/tree.c:3037
netlink: 24 bytes leftover after parsing attributes in process `syz-executor5'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor5'.
netlink: 24 bytes leftover after parsing attributes in process `syz-executor5'.

stack backtrace:
CPU: 0 PID: 2043 Comm: udevd Not tainted 4.9.119-g9dc978d #23
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
 ffff8801db207d60 ffffffff81eb4be9 ffff8801ccb09800 0000000000000000
 0000000000000002 ffffffff83c6df20 ffff8801d0041a58 ffff8801db207d90
 ffffffff81426330 ffff8801d0041900 ffff8801cdcc6e48 ffff8801cdcc6648
Call Trace:
 <IRQ> [  350.857679]  [<ffffffff81eb4be9>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [  350.857679]  [<ffffffff81eb4be9>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff81426330>] lockdep_rcu_suspicious.cold.48+0x110/0x141 kernel/locking/lockdep.c:4455
 [<ffffffff81284148>] synchronize_rcu+0x68/0x90 kernel/rcu/tree_plugin.h:675
 [<ffffffff836bfe3a>] __l2tp_session_unhash+0x38a/0x520 net/l2tp/l2tp_core.c:1796
 [<ffffffff836c01c7>] l2tp_tunnel_closeall+0x1f7/0x350 net/l2tp/l2tp_core.c:1364
 [<ffffffff836c0a82>] l2tp_tunnel_destruct+0x2f2/0x590 net/l2tp/l2tp_core.c:1324
 [<ffffffff830230f5>] __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
 [<ffffffff83a038bb>] __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
 [<ffffffff83a024a1>] exiting_irq arch/x86/include/asm/apic.h:659 [inline]
 [<ffffffff83a024a1>] smp_apic_timer_interrupt+0x81/0xa0 arch/x86/kernel/apic/apic.c:960
 [<ffffffff839fe630>] apic_timer_interrupt+0xa0/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [  350.971276]  [<ffffffff8123acb3>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [  350.971276]  [<ffffffff8123acb3>] ? lock_acquire+0x173/0x3e0 kernel/locking/lockdep.c:3759
 [<ffffffff815c178b>] rcu_lock_acquire include/linux/rcupdate.h:493 [inline]
 [<ffffffff815c178b>] rcu_read_lock include/linux/rcupdate.h:875 [inline]
 [<ffffffff815c178b>] dput.part.29+0x6b/0x7b0 fs/dcache.c:798
 [<ffffffff815c1eef>] dput+0x1f/0x30 fs/dcache.c:792
 [<ffffffff815a12cb>] path_to_nameidata fs/namei.c:858 [inline]
 [<ffffffff815a12cb>] walk_component+0x2fb/0x1bb0 fs/namei.c:1808
 [<ffffffff815a3409>] link_path_walk+0x889/0x1200 fs/namei.c:2120
 [<ffffffff815a447d>] path_openat+0x1ad/0x3590 fs/namei.c:3533
 [<ffffffff815abb27>] do_filp_open+0x197/0x270 fs/namei.c:3568
 [<ffffffff8156e2fd>] do_sys_open+0x30d/0x5c0 fs/open.c:1072
 [<ffffffff8156e5dd>] SYSC_open fs/open.c:1090 [inline]
 [<ffffffff8156e5dd>] SyS_open+0x2d/0x40 fs/open.c:1085
 [<ffffffff81006316>] do_syscall_64+0x1a6/0x490 arch/x86/entry/common.c:282
 [<ffffffff839fccd3>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb
ODEBUG: object ffff8801db207ce8 is NOT on stack ffff8801ccb60000, but annotated
------------[ cut here ]------------
WARNING: CPU: 0 PID: 2043 at lib/debugobjects.c:303 debug_object_is_on_stack lib/debugobjects.c:303 [inline]
WARNING: CPU: 0 PID: 2043 at lib/debugobjects.c:303 __debug_object_init.cold.10+0x6b/0x2b0 lib/debugobjects.c:329