Recap of Buffer Overflow Protection


Attacker cannot overwrite return address; must guess 32 bit random number

Attacker has no memory he can write to, which also permits execution

Various data are no longer executable

Stack, bss, and data segments are not executable

GOT/PLT tables W^X: cannot be modified by attacker

ESSENTIALLY NO PERFORMANCE LOSS.

Complete coverage on good cpus; hacks for weak ones

No violation of POSIX semantics