Linux kernel before 2.6.16.21 and 2.6.17, when running on PowerPC, does not perform certain required access_ok checks, which allows local users to read arbitrary kernel memory on 64-bit systems (signal_64.c) and cause a denial of service (crash) and possibly read kernel memory on 32-bit systems (signal_32.c).
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A10040
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=194215
http://www.vupen.com/english/advisories/2006/2451
http://www.ubuntu.com/usn/usn-311-1
http://www.trustix.org/errata/2006/0037
http://www.securityfocus.com/bid/18616
http://www.securityfocus.com/archive/1/438168/100/0/threaded
http://www.redhat.com/support/errata/RHSA-2006-0575.html
http://www.novell.com/linux/security/advisories/2006_47_kernel.html
http://www.novell.com/linux/security/advisories/2006_42_kernel.html
http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.16.21
http://support.avaya.com/elmodocs2/security/ASA-2006-200.htm
http://secunia.com/advisories/22417
http://secunia.com/advisories/21498
http://secunia.com/advisories/21465
http://secunia.com/advisories/21179
http://secunia.com/advisories/20991