Linux 2.6.11 on 64-bit x86 (x86_64) platforms does not use a guard page for the 47-bit address page to protect against an AMD K8 bug, which allows local users to cause a denial of service.
https://exchange.xforce.ibmcloud.com/vulnerabilities/43324
http://www.securityfocus.com/bid/13904
http://www.mandriva.com/security/advisories?name=MDKSA-2005:220