CVE 2006-1522
The sys_add_key function in the keyring code in Linux kernel 2.6.16.1 and 2.6.17-rc1, and possibly earlier versions, allows local users to cause a denial of service (OOPS) via keyctl requests that add a key to a user key instead of a keyring key, which causes an invalid dereference in the __keyring_
See the 
CVE page on Mitre.org
for more details.
