IPv6: ADDRCONF(NETDEV_UP): veth1: link is not ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth1: link becomes ready
IPv6: ADDRCONF(NETDEV_CHANGE): veth0: link becomes ready

============================================
WARNING: possible recursive locking detected
4.16.0-rc7+ #370 Not tainted
--------------------------------------------
syzkaller507490/5710 is trying to acquire lock:
 (rtnl_mutex){+.+.}, at: [<0000000047f3961b>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74

but task is already holding lock:
 (rtnl_mutex){+.+.}, at: [<0000000047f3961b>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(rtnl_mutex);
  lock(rtnl_mutex);

 *** DEADLOCK ***

 May be due to missing lock nesting notation

2 locks held by syzkaller507490/5710:
 #0:  (rtnl_mutex){+.+.}, at: [<0000000047f3961b>] rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
 #1:  (ipvs->sync_mutex){+.+.}, at: [<000000002b2926a2>] do_ip_vs_set_ctl+0x10f8/0x1cc0 net/netfilter/ipvs/ip_vs_ctl.c:2388

stack backtrace:
CPU: 1 PID: 5710 Comm: syzkaller507490 Not tainted 4.16.0-rc7+ #370
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Call Trace:
 __dump_stack lib/dump_stack.c:17 [inline]
 dump_stack+0x194/0x24d lib/dump_stack.c:53
 print_deadlock_bug kernel/locking/lockdep.c:1761 [inline]
 check_deadlock kernel/locking/lockdep.c:1805 [inline]
 validate_chain kernel/locking/lockdep.c:2401 [inline]
 __lock_acquire+0xe8f/0x3e00 kernel/locking/lockdep.c:3431
 lock_acquire+0x1d5/0x580 kernel/locking/lockdep.c:3920
 __mutex_lock_common kernel/locking/mutex.c:756 [inline]
 __mutex_lock+0x16f/0x1a80 kernel/locking/mutex.c:893
 mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
 rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
 ip_mc_drop_socket+0x88/0x230 net/ipv4/igmp.c:2643
 inet_release+0x4e/0x1c0 net/ipv4/af_inet.c:413
 sock_release+0x8d/0x1e0 net/socket.c:595
 start_sync_thread+0x2213/0x2b70 net/netfilter/ipvs/ip_vs_sync.c:1924
 do_ip_vs_set_ctl+0x1139/0x1cc0 net/netfilter/ipvs/ip_vs_ctl.c:2389
 nf_sockopt net/netfilter/nf_sockopt.c:106 [inline]
 nf_setsockopt+0x67/0xc0 net/netfilter/nf_sockopt.c:115
 ip_setsockopt+0x97/0xa0 net/ipv4/ip_sockglue.c:1261
 raw_setsockopt+0xb7/0xd0 net/ipv4/raw.c:870
 sock_common_setsockopt+0x95/0xd0 net/core/sock.c:2975
 SYSC_setsockopt net/socket.c:1849 [inline]
 SyS_setsockopt+0x189/0x360 net/socket.c:1828
 do_syscall_64+0x281/0x940 arch/x86/entry/common.c:287
 entry_SYSCALL_64_after_hwframe+0x42/0xb7
RIP: 0033:0x447c19
RSP: 002b:00007f7c9e3e8d28 EFLAGS: 00000246 ORIG_RAX: 0000000000000036
RAX: ffffffffffffffda RBX: 00000000006e3a00 RCX: 0000000000447c19
RDX: 000000000000048b RSI: 0000000000000000 RDI: 0000000000000003
RBP: 00000000006e3a04 R08: 0000000000000018 R09: 0000000000000000
R10: 0000000020000100 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffee02c86cf R14: 00007f7c9e3e99c0 R15: 00000000006e3b80