CVE-2022-48910 net: ipv6: ensure we call ipv6_mc_down() at most once

In the Linux kernel, the following vulnerability has been resolved: net: ipv6: ensure we call ipv6mcdown at most once There are two reasons for addrconfnotify to be called with NETDEVDOWN: either the network device is actually going down, or IPv6 was disabled on the interface. If either of them...