The Linux kernel through 3.17.4 does not properly restrict dropping of supplemental group memberships in certain namespace scenarios, which allows local users to bypass intended file permissions by leveraging a POSIX ACL containing an entry for the group category that is more restrictive than the entry for the other category, aka a negative groups issue, related to kernel/groups.c, kernel/uid16.c, and kernel/user_namespace.c. http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2014-8989
