This whitepaper is the Linux Exploit Writing Tutorial Part 3 – ret2libc. This is revision 2 of this paper.
You can download it from the following link: https://packetstormsecurity.com/files/download/100738/lewt3rev2-ret2libc.pdf
Source: https://packetstormsecurity.com/files/100738/Linux-Exploit-Writing-Tutorial-Part-3-Revision-2.html