The Radeon GPU drivers in the Linux kernel before 2.6.38-rc5 do not properly validate data related to the AA resolve registers, which allows local users to write to arbitrary memory locations associated with (1) Video RAM (aka VRAM) or (2) the Graphics Translation Table (GTT) via crafted values.
https://exchange.xforce.ibmcloud.com/vulnerabilities/65691
https://bugzilla.redhat.com/show_bug.cgi?id=680000
http://www.securityfocus.com/bid/46557
http://openwall.com/lists/oss-security/2011/02/25/4
http://openwall.com/lists/oss-security/2011/02/24/3