The BPFSANCNLATTRNEST extension implementation in the skrunfilter function in net/core/filter.c in the Linux kernel through 3.14.3 uses the reverse order in a certain subtraction, which allows local users to cause a denial of service (over-read and system crash) via crafted BPF instructions. NOTE: the affected code was moved to the _skbgetnlattrnest function before the vulnerability was announced.