The key serial number collision avoidance code in the key_alloc_serial function in Linux kernel 2.6.9 up to 2.6.20 allows local users to cause a denial of service (crash) via vectors that trigger a null dereference, as originally reported as "spinlock CPU recursion."
https://oval.cisecurity.org/repository/search/definition/oval%3Aorg.mitre.oval%3Adef%3A9829
https://issues.rpath.com/browse/RPL-1097
https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=227495
http://www.ubuntu.com/usn/usn-451-1
http://www.securityfocus.com/bid/22539
http://www.securityfocus.com/archive/1/471457
http://www.redhat.com/support/errata/RHSA-2007-0099.html
http://www.redhat.com/support/errata/RHSA-2007-0085.html
http://www.novell.com/linux/security/advisories/2007_21_kernel.html
http://www.mandriva.com/security/advisories?name=MDKSA-2007:060
http://www.mandriva.com/security/advisories?name=MDKSA-2007:047
http://secunia.com/advisories/25691
http://secunia.com/advisories/24752
http://secunia.com/advisories/24547
http://secunia.com/advisories/24482
http://secunia.com/advisories/24429
http://secunia.com/advisories/24300
http://secunia.com/advisories/24259