mm/ioremap.c in Linux 2.6 on 64-bit x86 systems allows local users to cause a denial of service or an information leak via an ioremap on a certain memory map that causes the iounmap to perform a lookup of a page that does not exist.
Ubuntu Security Notice USN-199-1 - Multiple vulnerabilities exist in both linux-source-2.6.10 and linux-source-2.6.8. These include race conditions and denial of service flaws.