===============================
[ INFO: suspicious RCU usage. ]
4.9.155+ #27 Not tainted
-------------------------------
net/ipv6/ip6_fib.c:1470 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
6 locks held by syz-executor.3/3211:
 #0:  (tasklist_lock){.+.+..}, at: [<ffffffff810eb861>] do_wait+0x371/0x930 kernel/exit.c:1566
 #1:  (rcu_read_lock){......}, at: [<ffffffff819fd000>] task_has_perm+0x0/0x330 security/selinux/hooks.c:5822
 #2:  (((&net->ipv6.ip6_fib_timer))){+.-...}, at: [<ffffffff812624fe>] lockdep_copy_map include/linux/lockdep.h:165 [inline]
 #2:  (((&net->ipv6.ip6_fib_timer))){+.-...}, at: [<ffffffff812624fe>] call_timer_fn+0xde/0x6d0 kernel/time/timer.c:1309
 #3:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-...}, at: [<ffffffff826ef1e2>] spin_lock_bh include/linux/spinlock.h:307 [inline]
 #3:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-...}, at: [<ffffffff826ef1e2>] fib6_run_gc+0xa2/0x2e0 net/ipv6/ip6_fib.c:1816
 #4:  (rcu_read_lock){......}, at: [<ffffffff826e69f0>] __fib6_clean_all+0x0/0x230 net/ipv6/ip6_fib.c:1703
 #5:  (&tb->tb6_lock){++--..}, at: [<ffffffff826e6ad3>] __fib6_clean_all+0xe3/0x230 net/ipv6/ip6_fib.c:1717

stack backtrace:
CPU: 0 PID: 3211 Comm: syz-executor.3 Not tainted 4.9.155+ #27
 ffff8801db607890 ffffffff81b47871 ffff8801d698ea80 0000000000000000
 0000000000000002 00000000000005be ffff8801c9abc740 ffff8801db6078c0
 ffffffff813fed99 ffff8801db607ae0 dffffc0000000000 00000000ffffffff
Call Trace:
 <IRQ> [ 3326.647529]  [<ffffffff81b47871>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [ 3326.647529]  [<ffffffff81b47871>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813fed99>] lockdep_rcu_suspicious.cold+0x10a/0x149 kernel/locking/lockdep.c:4455
 [<ffffffff826ee93f>] fib6_del+0x81f/0xb20 net/ipv6/ip6_fib.c:1470
 [<ffffffff826eeedc>] fib6_clean_node+0x29c/0x4d0 net/ipv6/ip6_fib.c:1657
 [<ffffffff826e62c0>] fib6_walk_continue+0x3e0/0x630 net/ipv6/ip6_fib.c:1583
 [<ffffffff826e687d>] fib6_walk+0x9d/0xf0 net/ipv6/ip6_fib.c:1628
 [<ffffffff826e69b7>] fib6_clean_tree+0xe7/0x120 net/ipv6/ip6_fib.c:1702
 [<ffffffff826e6aeb>] __fib6_clean_all+0xfb/0x230 net/ipv6/ip6_fib.c:1718
 [<ffffffff826ef264>] fib6_clean_all net/ipv6/ip6_fib.c:1729 [inline]
 [<ffffffff826ef264>] fib6_run_gc+0x124/0x2e0 net/ipv6/ip6_fib.c:1826
 [<ffffffff826ef43d>] fib6_gc_timer_cb+0x1d/0x30 net/ipv6/ip6_fib.c:1841
 [<ffffffff81262587>] call_timer_fn+0x167/0x6d0 kernel/time/timer.c:1319
 [<ffffffff81262d4b>] expire_timers+0x25b/0x5c0 kernel/time/timer.c:1359
 [<ffffffff812632af>] __run_timers kernel/time/timer.c:1674 [inline]
 [<ffffffff812632af>] run_timer_softirq+0x1ff/0x620 kernel/time/timer.c:1687
 [<ffffffff8281be7d>] __do_softirq+0x22d/0x964 kernel/softirq.c:288
 [<ffffffff810eecd9>] invoke_softirq kernel/softirq.c:368 [inline]
 [<ffffffff810eecd9>] irq_exit+0x119/0x160 kernel/softirq.c:409
 [<ffffffff8281a9be>] exiting_irq arch/x86/include/asm/apic.h:669 [inline]
 [<ffffffff8281a9be>] smp_apic_timer_interrupt+0x7e/0xb0 arch/x86/kernel/apic/apic.c:962
 [<ffffffff8281822d>] apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [ 3326.912919]  [<ffffffff8120c4d6>] ? arch_local_irq_restore arch/x86/include/asm/paravirt.h:768 [inline]
 <EOI> [ 3326.912919]  [<ffffffff8120c4d6>] ? lock_acquire+0x176/0x3d0 kernel/locking/lockdep.c:3759
 [<ffffffff819fd04a>] rcu_lock_acquire include/linux/rcupdate.h:493 [inline]
 [<ffffffff819fd04a>] rcu_read_lock include/linux/rcupdate.h:875 [inline]
 [<ffffffff819fd04a>] task_has_perm+0x4a/0x330 security/selinux/hooks.c:1611
 [<ffffffff819fd354>] selinux_task_wait+0x24/0x30 security/selinux/hooks.c:3954
 [<ffffffff819ec0c3>] security_task_wait+0x73/0xb0 security/security.c:1039
 [<ffffffff810e81a4>] wait_consider_task+0x294/0x35e0 kernel/exit.c:1385
 [<ffffffff810eb8ec>] do_wait_thread kernel/exit.c:1498 [inline]
 [<ffffffff810eb8ec>] do_wait+0x3fc/0x930 kernel/exit.c:1569
 [<ffffffff810ec944>] SYSC_wait4 kernel/exit.c:1701 [inline]
 [<ffffffff810ec944>] SyS_wait4+0x144/0x210 kernel/exit.c:1666
 [<ffffffff810056bd>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<ffffffff82816a93>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb