Mandriva Linux Security Advisory 2009-233 – The Linux kernel 2.6.0 through 2.6.30.4, and 2.4.4 through 2.4.37.4, does not initialize all function pointers for socket operations in proto_ops structures, which allows local users to trigger a NULL pointer dereference and gain privileges by using mmap to map page zero, placing arbitrary code on this page, and then invoking an unavailable operation, as demonstrated by the sendpage operation on a PF_PPPOX socket.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/81306/MDVSA-2009-233.txt
Source: https://packetstormsecurity.com/files/81306/Mandriva-Linux-Security-Advisory-2009-233.html