Messages in this thread | | | Date | Thu, 7 Aug 1997 20:47:33 +0200 (METDST) | From | Gabriel Paubert <> | Subject | Re: other platforms and Linux compile... |
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On Thu, 7 Aug 1997, Albert D. Cahalan wrote:
> Doesn't that eliminate most stack smashing exploits? > You can only hit function pointers, not the return address. > Most overwrites would fill empty stack space until the > stack limit is exceeded. > > This looks better than preventing stack execution. > > With the PowerPC binary compatibility, that would mean > the stack grows up on normal PowerMac Linux too, right?
No, it grows down on all PPC API I know of (SYSV and PowerOpen).
> I think I recall a flag in the Intel CPU to do that too.
You are probably getting confused by the expand-down flag in the segment descriptors. It just controls whether the valid address are either between 0 and the limit or between the limit and the maximum size. On Intel the stack grows down (pushes and calls decrement the stack pointer, pops and ret increment it).
Gabriel.
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