The sock_alloc_send_pskb function in net/core/sock.c in the Linux kernel before 3.4.5 does not properly validate a certain length value, which allows local users to cause a denial of service (heap-based buffer overflow and system crash) or possibly gain privileges by leveraging access to a TUN/TAP device.
https://bugzilla.redhat.com/show_bug.cgi?id=816289
http://www.ubuntu.com/usn/USN-1535-1
http://www.securityfocus.com/bid/53721
http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.4.5
http://ubuntu.com/usn/usn-1529-1
http://secunia.com/advisories/50807