The BPF_S_ANC_NLATTR_NEST extension implementation in the sk_run_filter 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 __skb_get_nlattr_nest function before the vulnerability was announced.