"Strong" stack protection for GCC [LWN.net]

"Strong" stack protection for GCC

Posted Feb 7, 2014 18:19 UTC (Fri) by deater (subscriber, #11746)
In reply to: "Strong" stack protection for GCC by jzbiciak
Parent article: "Strong" stack protection for GCC

> On a machine whose stack grows up instead of down (Alpha was one such
> architecture),

I'm pretty sure the stack grows down on Alpha systems.

You might be thinking of HP PA-RISC where the stack grows up.

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"Strong" stack protection for GCC

Posted Feb 7, 2014 21:21 UTC (Fri) by jzbiciak (guest, #5246) [Link]

Quite possibly. For some reason I had it cached in my head that Alpha grew upwards. I tried to look it up, and found it's a surprisingly difficult topic to Google! Terms like "alpha", "stack" and "direction" turn up a lot of noise.

I did find a BUGTRAQ posting that indicates that the return value is stored below the other variables in a local stack frame, so the effect would be similar despite the stack itself growing down. If that's the case, that could be what I'm remembering.

The principle holds more generally that the frame you smash to trigger an exploit may not be the frame that holds the original array.