Stack Overflow Protection

6 Dec 2003

      Hello,

on http://lists.suse.com/archive/suse-security/2003-Dec/0051.html I read
that the SuSE 9.0 update kernel contains Stack Overflow Protection. I
tested this with a short example from an article in the German computer
magazine c't ("Das Sicherheitsloch", c't 23/2001, p. 216)

  1 void function(int a, int b, int c) {
  2    char buffer1[8];
  3    char buffer2[16];
  4    int *ret;
  5 
  6    ret = buffer1 + 12;
  7    (*ret) += 8;
  8 }
  9 
 10 void main() {
 11   int x;
 12 
 13   x = 0;
 14   function(1,2,3);
 15   x = 1;
 16   printf("%d\n",x);
 17 }

On SuSE 9.0 this produces "1", which is correct, on an old machine it
produces "0", which is incorrect. 

My questions are now:

 1. Does this protection have any disadvantages?
 2. Will it be included in future versions of the vanilla kernel?
 3. Why is this a "hidden feature"? Why doesn't SuSE let the people know
    that they've included this stack overflow protection?

Regards,
Bernhard

Stack Overflow Protection

Bernhard Walle