===============================
[ INFO: suspicious RCU usage. ]
4.4.171+ #12 Not tainted
-------------------------------
net/ipv6/ip6_fib.c:1465 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 1, debug_locks = 0
4 locks held by swapper/0/0:
 #0:  (((&net->ipv6.ip6_fib_timer))){+.-...}, at: [<ffffffff8125801e>] lockdep_copy_map include/linux/lockdep.h:165 [inline]
 #0:  (((&net->ipv6.ip6_fib_timer))){+.-...}, at: [<ffffffff8125801e>] call_timer_fn+0xde/0x850 kernel/time/timer.c:1175
 #1:  (fib6_gc_lock){+.-...}, at: [<ffffffff825f95ea>] spin_lock_bh include/linux/spinlock.h:307 [inline]
 #1:  (fib6_gc_lock){+.-...}, at: [<ffffffff825f95ea>] fib6_run_gc+0x3a/0x230 net/ipv6/ip6_fib.c:1811
 #2:  (rcu_read_lock){......}, at: [<ffffffff825f1190>] __fib6_clean_all+0x0/0x240 net/ipv6/ip6_fib.c:1698
 #3:  (&tb->tb6_lock){++--..}, at: [<ffffffff825f1278>] __fib6_clean_all+0xe8/0x240 net/ipv6/ip6_fib.c:1712

stack backtrace:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.4.171+ #12
 0000000000000000 5f0b3a0630c9f39f ffff8801db607940 ffffffff81aacd31
 ffff8801cfd0fc00 0000000000000000 0000000000000001 00000000000005b9
 ffffffff82e151c0 ffff8801db607970 ffffffff813ab5d0 ffff8801db607b90
Call Trace:
 <IRQ>  [<ffffffff81aacd31>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ>  [<ffffffff81aacd31>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813ab5d0>] lockdep_rcu_suspicious.cold+0x10a/0x149 kernel/locking/lockdep.c:4305
 [<ffffffff825f8d8a>] fib6_del+0x7ea/0xae0 net/ipv6/ip6_fib.c:1465
 [<ffffffff825f931c>] fib6_clean_node+0x29c/0x500 net/ipv6/ip6_fib.c:1652
 [<ffffffff825f0ae0>] fib6_walk_continue+0x3e0/0x630 net/ipv6/ip6_fib.c:1578
 [<ffffffff825f1021>] fib6_walk+0x91/0xe0 net/ipv6/ip6_fib.c:1623
 [<ffffffff825f1158>] fib6_clean_tree+0xe8/0x120 net/ipv6/ip6_fib.c:1697
 [<ffffffff825f1290>] __fib6_clean_all+0x100/0x240 net/ipv6/ip6_fib.c:1713
 [<ffffffff825f965f>] fib6_clean_all net/ipv6/ip6_fib.c:1724 [inline]
 [<ffffffff825f965f>] fib6_run_gc+0xaf/0x230 net/ipv6/ip6_fib.c:1821
 [<ffffffff825f97fd>] fib6_gc_timer_cb+0x1d/0x30 net/ipv6/ip6_fib.c:1836
 [<ffffffff812580cd>] call_timer_fn+0x18d/0x850 kernel/time/timer.c:1185
 [<ffffffff81258caf>] __run_timers kernel/time/timer.c:1261 [inline]
 [<ffffffff81258caf>] run_timer_softirq+0x51f/0xb70 kernel/time/timer.c:1444
 [<ffffffff8271af56>] __do_softirq+0x226/0xa3f kernel/softirq.c:273
 [<ffffffff810e187a>] invoke_softirq kernel/softirq.c:350 [inline]
 [<ffffffff810e187a>] irq_exit+0x10a/0x150 kernel/softirq.c:391
 [<ffffffff8271a68e>] exiting_irq arch/x86/include/asm/apic.h:652 [inline]
 [<ffffffff8271a68e>] smp_apic_timer_interrupt+0x7e/0xb0 arch/x86/kernel/apic/apic.c:926
 [<ffffffff827199dd>] apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:768
 <EOI>  [<ffffffff810a1dc2>] ? native_safe_halt+0x2/0x10 arch/x86/include/asm/irqflags.h:52
 [<ffffffff81022d50>] arch_cpu_idle+0x10/0x20 arch/x86/kernel/process.c:423
 [<ffffffff811eb2b8>] default_idle_call+0x48/0x70 kernel/sched/idle.c:93
 [<ffffffff811eba91>] cpuidle_idle_call kernel/sched/idle.c:157 [inline]
 [<ffffffff811eba91>] cpu_idle_loop kernel/sched/idle.c:253 [inline]
 [<ffffffff811eba91>] cpu_startup_entry+0x6d1/0x810 kernel/sched/idle.c:301
 [<ffffffff82704cc9>] rest_init+0x190/0x199 init/main.c:410
 [<ffffffff831d58a0>] start_kernel+0x64a/0x67e init/main.c:682
 [<ffffffff831d430a>] x86_64_start_reservations+0x29/0x2b arch/x86/kernel/head64.c:196
 [<ffffffff831d4443>] x86_64_start_kernel+0x137/0x15a arch/x86/kernel/head64.c:185
audit: type=1400 audit(1548485390.254:66): avc:  denied  { create } for  pid=17220 comm="syz-executor2" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:mail_spool_t:s0 tclass=tcp_socket permissive=1
audit: type=1400 audit(1548485390.284:67): avc:  denied  { bind } for  pid=17220 comm="syz-executor2" scontext=unconfined_u:system_r:insmod_t:s0-s0:c0.c1023 tcontext=system_u:object_r:mail_spool_t:s0 tclass=tcp_socket permissive=1
audit: type=1400 audit(1548485390.304:68): avc:  denied  { node_bind } for  pid=17220 comm="syz-executor2" scontext=system_u:object_r:mail_spool_t:s0 tcontext=system_u:object_r:node_t:s0 tclass=tcp_socket permissive=1
nla_parse: 1 callbacks suppressed
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
nla_parse: 16 callbacks suppressed
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.
netlink: 8 bytes leftover after parsing attributes in process `syz-executor4'.