Please take a look at on this exploit: http://blog.zx2c4.com/749 It is interesting to think about /proc/pid/mem protection and about building su with PIE enabled...
Regards: Dw. -- dr Tóth Attila, Radiológus, 06-20-825-8057 Attila Toth MD, Radiologist, +36-20-825-8057