unregister_netdevice: waiting for lo to become free. Usage count = 2
leaked reference.
 __netdev_tracker_alloc include/linux/netdevice.h:4020 [inline]
 netdev_hold include/linux/netdevice.h:4049 [inline]
 ipv6_add_dev+0x14c/0x560 net/ipv6/addrconf.c:401
 addrconf_notify+0x1ec/0x724 net/ipv6/addrconf.c:3552
 notifier_call_chain+0x64/0xe0 kernel/notifier.c:87
 raw_notifier_call_chain+0x20/0x28 kernel/notifier.c:455
 call_netdevice_notifiers_info+0x58/0xa0 net/core/dev.c:1944
 call_netdevice_notifiers_extack net/core/dev.c:1982 [inline]
 call_netdevice_notifiers net/core/dev.c:1996 [inline]
 register_netdevice+0x44c/0x61c net/core/dev.c:10078
 register_netdev+0x24/0x3c net/core/dev.c:10173
 loopback_net_init+0x4c/0xa4 drivers/net/loopback.c:219
 ops_init+0x40/0x11c net/core/net_namespace.c:135
 setup_net+0x1cc/0x3b8 net/core/net_namespace.c:333
 copy_net_ns+0xf8/0x268 net/core/net_namespace.c:483
 create_new_namespaces+0x10c/0x2a4 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0x70/0x8c kernel/nsproxy.c:228
 ksys_unshare+0x184/0x370 kernel/fork.c:3202
 __do_sys_unshare kernel/fork.c:3273 [inline]
 sys_unshare+0x10/0x14 kernel/fork.c:3271
 ret_fast_syscall+0x0/0x1c arch/arm/mm/proc-v7.S:66