chkstat in SuSE Linux 9.0 through 10.0 allows local users to modify permissions of files by creating a hardlink to a file from a world-writable directory, which can cause the link count to drop to 1 when the file is deleted or replaced, which is then modified by chkstat to use weaker permissions.
https://exchange.xforce.ibmcloud.com/vulnerabilities/22853
http://www.securityfocus.com/bid/15182
http://www.novell.com/linux/security/advisories/2005_62_permissions.html