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. A flaw was found in the way the Linux kernel"s splice system call validated its parameters. On certain file systems, a local, unprivileged user could use this flaw to write past the maximum file size, and thus crash the system