The Linux kernel before 3.15.4 on Intel processors does not properly restrict use of a non-canonical value for the saved RIP address in the case of a system call that does not use IRET, which allows local users to leverage a race condition and gain privileges, or cause a denial of service (double fault), via a crafted application that makes ptrace and fork system calls.
https://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.4.97
https://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.14.11
https://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.10.47
https://github.com/torvalds/linux/commit/b9cd18de4db3c9ffa7e17b0dc0ca99ed5aa4d43a
https://bugzilla.redhat.com/show_bug.cgi?id=1115927
http://www.ubuntu.com/usn/USN-2274-1
http://www.ubuntu.com/usn/USN-2273-1
http://www.ubuntu.com/usn/USN-2272-1
http://www.ubuntu.com/usn/USN-2271-1
http://www.ubuntu.com/usn/USN-2270-1
http://www.ubuntu.com/usn/USN-2269-1
http://www.ubuntu.com/usn/USN-2268-1
http://www.ubuntu.com/usn/USN-2267-1
http://www.ubuntu.com/usn/USN-2266-1
http://www.openwall.com/lists/oss-security/2014/07/04/4
http://www.kernel.org/pub/linux/kernel/v3.x/ChangeLog-3.15.4
http://www.debian.org/security/2014/dsa-2972
http://secunia.com/advisories/60393
http://secunia.com/advisories/60380
http://secunia.com/advisories/60220
http://secunia.com/advisories/59654
http://secunia.com/advisories/59639
http://secunia.com/advisories/59633
http://openwall.com/lists/oss-security/2014/07/08/5
http://openwall.com/lists/oss-security/2014/07/08/16
http://openwall.com/lists/oss-security/2014/07/05/4
http://linux.oracle.com/errata/ELSA-2014-3048.html