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.
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A11322
http://www.ubuntu.com/usn/usn-199-1
http://www.securityfocus.com/bid/15049
http://www.redhat.com/support/errata/RHSA-2005-808.html
http://www.debian.org/security/2005/dsa-922
http://secunia.com/advisories/18056