random: crng init done
netlink: 8 bytes leftover after parsing attributes in process `syz-executor580'.
===============================
[ 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
4 locks held by syz-executor580/2072:
 #0:  (rtnl_mutex){+.+.+.}, at: [<ffffffff82343527>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.....}, at: [<ffffffff826ef36c>] spin_trylock_bh include/linux/spinlock.h:367 [inline]
 #1:  (&(&net->ipv6.fib6_gc_lock)->rlock){+.....}, at: [<ffffffff826ef36c>] fib6_run_gc+0x22c/0x2e0 net/ipv6/ip6_fib.c:1817
 #2:  (rcu_read_lock){......}, at: [<ffffffff826e69f0>] __fib6_clean_all+0x0/0x230 net/ipv6/ip6_fib.c:1703
 #3:  (&tb->tb6_lock){++....}, at: [<ffffffff826e6ad3>] __fib6_clean_all+0xe3/0x230 net/ipv6/ip6_fib.c:1717

stack backtrace:
CPU: 0 PID: 2072 Comm: syz-executor580 Not tainted 4.9.155+ #27
 ffff8801ce2d7470 ffffffff81b47871 ffff8801ce8b0380 0000000000000000
 0000000000000002 00000000000005be ffff8801d25a5f00 ffff8801ce2d74a0
 ffffffff813fed99 ffff8801ce2d76c0 dffffc0000000000 00000000ffffffff
Call Trace:
 [<ffffffff81b47871>] __dump_stack lib/dump_stack.c:15 [inline]
 [<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
 [<ffffffff826fa86b>] ndisc_netdev_event+0x2ab/0x350 net/ipv6/ndisc.c:1750
 [<ffffffff81146e34>] notifier_call_chain+0xb4/0x1d0 kernel/notifier.c:93
 [<ffffffff81146fbe>] __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 [<ffffffff81146fbe>] raw_notifier_call_chain+0x2e/0x40 kernel/notifier.c:401
 [<ffffffff822f7586>] call_netdevice_notifiers_info+0x56/0x70 net/core/dev.c:1647
 [<ffffffff822f8283>] call_netdevice_notifiers net/core/dev.c:1663 [inline]
 [<ffffffff822f8283>] dev_close_many+0x2f3/0x6a0 net/core/dev.c:1456
 [<ffffffff82305c20>] rollback_registered_many+0x3a0/0xb50 net/core/dev.c:6838
 [<ffffffff823064c2>] rollback_registered+0xf2/0x1b0 net/core/dev.c:6901
 [<ffffffff8230fd1e>] unregister_netdevice_queue net/core/dev.c:7888 [inline]
 [<ffffffff8230fd1e>] unregister_netdevice_queue+0x1ae/0x230 net/core/dev.c:7881
 [<ffffffff81ed5810>] unregister_netdevice include/linux/netdevice.h:2468 [inline]
 [<ffffffff81ed5810>] __tun_detach+0x820/0xa00 drivers/net/tun.c:575
 [<ffffffff81ed5a36>] tun_detach drivers/net/tun.c:585 [inline]
 [<ffffffff81ed5a36>] tun_chr_close+0x46/0x60 drivers/net/tun.c:2392
 [<ffffffff81512344>] __fput+0x274/0x720 fs/file_table.c:208
 [<ffffffff81512876>] ____fput+0x16/0x20 fs/file_table.c:244
 [<ffffffff8113cf88>] task_work_run+0x108/0x180 kernel/task_work.c:116
 [<ffffffff810e5bbb>] exit_task_work include/linux/task_work.h:21 [inline]
 [<ffffffff810e5bbb>] do_exit+0x78b/0x2aa0 kernel/exit.c:841
 [<ffffffff810ec2c1>] do_group_exit+0x111/0x300 kernel/exit.c:945
 [<ffffffff810ec4cd>] SYSC_exit_group kernel/exit.c:956 [inline]
 [<ffffffff810ec4cd>] SyS_exit_group+0x1d/0x20 kernel/exit.c:954
 [<fffffff