The osf_wait4 function in arch/alpha/kernel/osf_sys.c in the Linux kernel before 2.6.39.4 on the Alpha platform uses an incorrect pointer, which allows local users to gain privileges by writing a certain integer value to kernel memory.
http://www.openwall.com/lists/oss-security/2011/06/15/7
http://ftp.osuosl.org/pub/linux/kernel/v2.6/ChangeLog-2.6.39.4