The assoc_array_gc function in the associative-array implementation in lib/assoc_array.c in the Linux kernel before 3.16.3 does not properly implement garbage collection, which allows local users to cause a denial of service (NULL pointer dereference and system crash) or possibly have unspecified other impact via multiple "keyctl newring" operations followed by a "keyctl timeout" operation.
https://bugzilla.redhat.com/show_bug.cgi?id=1140325
http://www.ubuntu.com/usn/USN-2379-1
http://www.ubuntu.com/usn/USN-2378-1