net: ipv6: ensure we call ipv6mcdown() at most once
This is an automated ID intended to aid in discovery of potential security vulnerabilities. The actual impact and attack plausibility have not yet been proven. This ID is fixed in Linux Kernel version v5.15.27 by commit b11781515208dd31fbcd0b664078dce5dc44523f, it was introduced in version v3.18 by commit 3ce62a84d53cd3d3cc5377bbf339e9b08ddf9c36. For more details please see the references link.