The eHCA driver in Linux kernel 2.6 before 2.6.22, when running on PowerPC, does not properly map userspace resources, which allows local users to read portions of physical address space.
http://rhn.redhat.com/errata/RHSA-2007-0940.html
http://secunia.com/advisories/27322
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10793