===============================
[ INFO: suspicious RCU usage. ]
4.9.112-g9e79039 #59 Not tainted
-------------------------------
net/ipv6/ip6_fib.c:1471 suspicious rcu_dereference_protected() usage!

other info that might help us debug this:


rcu_scheduler_active = 2, debug_locks = 0
6 locks held by kworker/u4:5/13005:
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118d09e>] work_static include/linux/workqueue.h:186 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118d09e>] set_work_data kernel/workqueue.c:617 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118d09e>] set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
 #0:  ("%s""netns"){.+.+.+}, at: [<ffffffff8118d09e>] process_one_work+0x6ee/0x1500 kernel/workqueue.c:2085
 #1:  (net_cleanup_work){+.+.+.}, at: [<ffffffff8118d0d8>] process_one_work+0x728/0x1500 kernel/workqueue.c:2089
 #2:  (net_mutex){+.+.+.}, at: [<ffffffff8305ca3f>] cleanup_net+0x13f/0x630 net/core/net_namespace.c:439
 #3:  (rtnl_mutex){+.+.+.}, at: [<ffffffff830b5937>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:70
 #4:  (rcu_read_lock){......}, at: [<ffffffff835a7c50>] __fib6_clean_all+0x0/0x220 net/ipv6/ip6_fib.c:1703
 #5:  (&tb->tb6_lock){++--..}, at: [<ffffffff835a7d30>] __fib6_clean_all+0xe0/0x220 net/ipv6/ip6_fib.c:1717

stack backtrace:
CPU: 1 PID: 13005 Comm: kworker/u4:5 Not tainted 4.9.112-g9e79039 #59
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: netns cleanup_net
 ffff8801a2b770b8 ffffffff81eb3249 ffff8801d4889800 0000000000000000
 0000000000000002 ffffffff84166880 ffffed003456ee66 ffff8801a2b770e8
 ffffffff814260f0 ffff8801cc14cc40 ffff8801a2b772e0 ffff8801cc14cc40
Call Trace:
 [<ffffffff81eb3249>] __dump_stack lib/dump_stack.c:15 [inline]
 [<ffffffff81eb3249>] dump_stack+0xc1/0x128 lib/dump_stack.c:51
 [<ffffffff814260f0>] lockdep_rcu_suspicious.cold.48+0x110/0x141 kernel/locking/lockdep.c:4455
 [<ffffffff835ae1e3>] fib6_del+0x773/0xa20 net/ipv6/ip6_fib.c:1470
 [<ffffffff835ae6b0>] fib6_clean_node+0x220/0x4c0 net/ipv6/ip6_fib.c:1657
 [<ffffffff835a5995>] fib6_walk_continue+0x3e5/0x640 net/ipv6/ip6_fib.c:1583
 [<ffffffff835a7ac9>] fib6_walk+0xd9/0x150 net/ipv6/ip6_fib.c:1628
 [<ffffffff835a7c13>] fib6_clean_tree+0xd3/0x110 net/ipv6/ip6_fib.c:1702
 [<ffffffff835a7d49>] __fib6_clean_all+0xf9/0x220 net/ipv6/ip6_fib.c:1718
 [<ffffffff835ae977>] fib6_clean_all+0x27/0x30 net/ipv6/ip6_fib.c:1729
 [<ffffffff835a4391>] rt6_ifdown+0xa1/0x7f0 net/ipv6/route.c:2716
 [<ffffffff8357efd0>] addrconf_ifdown+0xd0/0x10e0 net/ipv6/addrconf.c:3569
 [<ffffffff83586ad8>] addrconf_notify+0x7f8/0x2160 net/ipv6/addrconf.c:3493
 [<ffffffff811a18d4>] notifier_call_chain+0xb4/0x1d0 kernel/notifier.c:93
 [<ffffffff811a1a5d>] __raw_notifier_call_chain kernel/notifier.c:394 [inline]
 [<ffffffff811a1a5d>] raw_notifier_call_chain+0x2d/0x40 kernel/notifier.c:401
 [<ffffffff83068f85>] call_netdevice_notifiers_info+0x55/0x70 net/core/dev.c:1647
 [<ffffffff83069bb2>] call_netdevice_notifiers net/core/dev.c:1663 [inline]
 [<ffffffff83069bb2>] dev_close_many+0x252/0x380 net/core/dev.c:1456
 [<ffffffff8306ed58>] rollback_registered_many+0x268/0x920 net/core/dev.c:6810
 [<ffffffff830726ab>] unregister_netdevice_many.part.106+0x1b/0x110 net/core/dev.c:7879
 [<ffffffff83072b43>] unregister_netdevice_many net/core/dev.c:7878 [inline]
 [<ffffffff83072b43>] default_device_exit_batch+0x353/0x410 net/core/dev.c:8337
 [<ffffffff83059da5>] ops_exit_list.isra.6+0x105/0x160 net/core/net_namespace.c:139
 [<ffffffff8305cc21>] cleanup_net+0x321/0x630 net/core/net_namespace.c:473
 [<ffffffff8118d191>] process_one_work+0x7e1/0x1500 kernel/workqueue.c:2092
 [<ffffffff8118df86>] worker_thread+0xd6/0x10a0 kernel/workqueue.c:2226
 [<ffffffff8119d0bd>] kthread+0x26d/0x300 kernel/kthread.c:211
 [<ffffffff839fa11c>] ret_from_fork+0x5c/0x70 arch/x86/entry/entry_64.S:373