RedHat released a vulnerability today impacting PTRACE_SETREGS.  The release simply states: "A race conditon in ptrace can lead to kernel stack corruption and arbitrary kernel-mode code execution. A local unprivileged user could use this flaw to elavate his privileges."  It is being tracked as CVE-2013-0871.  A PoC was also posted at http://seclists.org/oss-sec/2013/q1/326.  According to the advisory, it impacts all Fedora versions.