The CVE states: "Hello, this is CVE-2015-1328 which allows a local root privilege escalation in the default configuration on all currently supported versions o

The CVE states: "Hello, this is CVE-2015-1328 which allows a local root privilege escalation in the default configuration on all currently supported versions of Ubuntu." But when I look in the /boot of a randomly picked Ubuntu 12.04 server, which has 3.2, 3.8 and 3.11 installed, only the corresponding config file for 3.2 has CONFIG_USER_NS. What happened to CONFIG_USER_NS in later kernel versions?