Local SELinux permission bypass via partial netlink validation

Authorization bypass in the Linux Foundation Linux Kernel before 5.7 allows local users to gain SELinux permissions via multi-message netlink buffers. The selinux_netlink_send hook validates only the first netlink message in an skb, then applies that decision to every remaining message without further checks. Low-privilege local access is required, and Red Hat reports no known abuse because modify operations require additional capabilities.