===============================
[ INFO: suspicious RCU usage. ]
4.9.154+ #21 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-executor1/31843:
 #0:  (sb_writers#6){.+.+.+}, at: [<ffffffff8150f9fa>] file_start_write include/linux/fs.h:2642 [inline]
 #0:  (sb_writers#6){.+.+.+}, at: [<ffffffff8150f9fa>] do_sendfile+0x93a/0xc00 fs/read_write.c:1392
 #1:  (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<ffffffff81412fba>] inode_lock include/linux/fs.h:768 [inline]
 #1:  (&sb->s_type->i_mutex_key#10){+.+.+.}, at: [<ffffffff81412fba>] generic_file_write_iter+0x9a/0x630 mm/filemap.c:2903
 #2:  (((&net->ipv6.ip6_fib_timer))){+.-...}, at: [<ffffffff812622ee>] lockdep_copy_map include/linux/lockdep.h:165 [inline]
 #2:  (((&net->ipv6.ip6_fib_timer))){+.-...}, at: [<ffffffff812622ee>] call_timer_fn+0xde/0x6d0 kernel/time/timer.c:1309
 #3:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-...}, at: [<ffffffff826eebf2>] spin_lock_bh include/linux/spinlock.h:307 [inline]
 #3:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.-...}, at: [<ffffffff826eebf2>] fib6_run_gc+0xa2/0x2e0 net/ipv6/ip6_fib.c:1816
 #4:  (rcu_read_lock){......}, at: [<ffffffff826e6400>] __fib6_clean_all+0x0/0x230 net/ipv6/ip6_fib.c:1703
 #5:  (&tb->tb6_lock){++--..}, at: [<ffffffff826e64e3>] __fib6_clean_all+0xe3/0x230 net/ipv6/ip6_fib.c:1717

stack backtrace:
CPU: 1 PID: 31843 Comm: syz-executor1 Not tainted 4.9.154+ #21
 ffff8801db707880 ffffffff81b47411 ffff8801d39ea540 0000000000000000
 0000000000000002 00000000000005be ffff8801a3c8c740 ffff8801db7078b0
 ffffffff813feb85 ffff8801db707ad0 dffffc0000000000 00000000ffffffff
Call Trace:
 <IRQ> [ 3362.540174]  [<ffffffff81b47411>] __dump_stack lib/dump_stack.c:15 [inline]
 <IRQ> [ 3362.540174]  [<ffffffff81b47411>] dump_stack+0xc1/0x120 lib/dump_stack.c:51
 [<ffffffff813feb85>] lockdep_rcu_suspicious.cold+0x10a/0x149 kernel/locking/lockdep.c:4455
 [<ffffffff826ee34f>] fib6_del+0x81f/0xb20 net/ipv6/ip6_fib.c:1470
 [<ffffffff826ee8ec>] fib6_clean_node+0x29c/0x4d0 net/ipv6/ip6_fib.c:1657
 [<ffffffff826e5cd0>] fib6_walk_continue+0x3e0/0x630 net/ipv6/ip6_fib.c:1583
 [<ffffffff826e628d>] fib6_walk+0x9d/0xf0 net/ipv6/ip6_fib.c:1628
 [<ffffffff826e63c7>] fib6_clean_tree+0xe7/0x120 net/ipv6/ip6_fib.c:1702
 [<ffffffff826e64fb>] __fib6_clean_all+0xfb/0x230 net/ipv6/ip6_fib.c:1718
 [<ffffffff826eec74>] fib6_clean_all net/ipv6/ip6_fib.c:1729 [inline]
 [<ffffffff826eec74>] fib6_run_gc+0x124/0x2e0 net/ipv6/ip6_fib.c:1826
 [<ffffffff826eee4d>] fib6_gc_timer_cb+0x1d/0x30 net/ipv6/ip6_fib.c:1841
 [<ffffffff81262377>] call_timer_fn+0x167/0x6d0 kernel/time/timer.c:1319
 [<ffffffff81262b3b>] expire_timers+0x25b/0x5c0 kernel/time/timer.c:1359
 [<ffffffff8126309f>] __run_timers kernel/time/timer.c:1674 [inline]
 [<ffffffff8126309f>] run_timer_softirq+0x1ff/0x620 kernel/time/timer.c:1687
 [<ffffffff8281b87d>] __do_softirq+0x22d/0x964 kernel/softirq.c:288
 [<ffffffff810eeac9>] invoke_softirq kernel/softirq.c:368 [inline]
 [<ffffffff810eeac9>] irq_exit+0x119/0x160 kernel/softirq.c:409
 [<ffffffff8281a50c>] exiting_irq arch/x86/include/asm/apic.h:669 [inline]
 [<ffffffff8281a50c>] smp_trace_apic_timer_interrupt+0x11c/0x540 arch/x86/kernel/apic/apic.c:983
 [<ffffffff82817cdd>] trace_apic_timer_interrupt+0x9d/0xb0 arch/x86/entry/entry_64.S:648
 <EOI> [ 3362.821252]  [<ffffffff8146157b>] ? constant_test_bit arch/x86/include/asm/bitops.h:311 [inline]
 <EOI> [ 3362.821252]  [<ffffffff8146157b>] ? PageUptodate include/linux/page-flags.h:419 [inline]
 <EOI> [ 3362.821252]  [<ffffffff8146157b>] ? shmem_getpage_gfp+0x26b/0x1b00 mm/shmem.c:1609
 [<ffffffff8146157b>] constant_test_bit arch/x86/include/asm/bitops.h:311 [inline]
 [<ffffffff8146157b>] PageUptodate include/linux/page-flags.h:419 [inline]
 [<ffffffff8146157b>] shmem_getpage_gfp+0x26b/0x1b00 mm/shmem.c:1609
 [<ffffffff81463748>] shmem_getpage mm/shmem.c:123 [inline]
 [<ffffffff81463748>] shmem_write_begin+0xf8/0x1a0 mm/shmem.c:2212
 [<ffffffff8140fd9a>] generic_perform_write+0x24a/0x500 mm/filemap.c:2753
 [<ffffffff81412d30>] __generic_file_write_iter+0x340/0x530 mm/filemap.c:2878
 [<ffffffff814132aa>] generic_file_write_iter+0x38a/0x630 mm/filemap.c:2906
 [<ffffffff81508f92>] vfs_iter_write+0x2e2/0x460 fs/read_write.c:390
 [<ffffffff815b0a29>] iter_file_splice_write+0x5a9/0xb10 fs/splice.c:768
 [<ffffffff815abd66>] do_splice_from fs/splice.c:870 [inline]
 [<ffffffff815abd66>] direct_splice_actor+0x126/0x1a0 fs/splice.c:1037
 [<ffffffff815adcd8>] splice_direct_to_actor+0x2c8/0x820 fs/splice.c:992
 [<ffffffff815ae3d5>] do_splice_direct+0x1a5/0x260 fs/splice.c:1080
 [<ffffffff8150f5c3>] do_sendfile+0x503/0xc00 fs/read_write.c:1393
 [<ffffffff81511541>] SYSC_sendfile64 fs/read_write.c:1448 [inline]
 [<ffffffff81511541>] SyS_sendfile64+0xd1/0x160 fs/read_write.c:1440
 [<ffffffff810056bd>] do_syscall_64+0x1ad/0x570 arch/x86/entry/common.c:285
 [<ffffffff82816493>] entry_SYSCALL_64_after_swapgs+0x5d/0xdb