Linux kernel 2.4 and 2.2 allows local users to read kernel memory and possibly gain privileges via a negative argument to the sysctl call.
https://exchange.xforce.ibmcloud.com/vulnerabilities/6079
http://www.securityfocus.com/bid/2364
http://www.redhat.com/support/errata/RHSA-2001-013.html
http://www.caldera.com/support/security/advisories/CSSA-2001-009.0.txt
http://archives.neohapsis.com/archives/bugtraq/2001-02/0267.html