unregister_netdevice: waiting for lo to become free. Usage count = 2
leaked reference.
 netdev_tracker_alloc include/linux/netdevice.h:3860 [inline]
 dev_hold_track include/linux/netdevice.h:3877 [inline]
 ipv6_add_dev net/ipv6/addrconf.c:408 [inline]
 ipv6_add_dev+0x416/0x11a0 net/ipv6/addrconf.c:375
 addrconf_notify+0x60e/0x1ba0 net/ipv6/addrconf.c:3523
 notifier_call_chain+0xb5/0x200 kernel/notifier.c:84
 call_netdevice_notifiers_info+0xb5/0x130 net/core/dev.c:1919
 call_netdevice_notifiers_extack net/core/dev.c:1931 [inline]
 call_netdevice_notifiers net/core/dev.c:1945 [inline]
 register_netdevice+0x10df/0x1580 net/core/dev.c:9698
 register_netdev+0x2d/0x50 net/core/dev.c:9791
 loopback_net_init+0x73/0x160 drivers/net/loopback.c:217
 ops_init+0xaf/0x470 net/core/net_namespace.c:140
 setup_net+0x554/0xbb0 net/core/net_namespace.c:330
 copy_net_ns+0x318/0x760 net/core/net_namespace.c:474
 create_new_namespaces+0x3f6/0xb20 kernel/nsproxy.c:110
 unshare_nsproxy_namespaces+0xc1/0x1f0 kernel/nsproxy.c:226
 ksys_unshare+0x445/0x920 kernel/fork.c:3058
 __do_sys_unshare kernel/fork.c:3129 [inline]
 __se_sys_unshare kernel/fork.c:3127 [inline]
 __x64_sys_unshare+0x2d/0x40 kernel/fork.c:3127
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae