Wireshark · Ethereal-dev: Re: [Ethereal-dev] Canary checking added to emem.c

[Gilbert Ramirez <gram@xxxxxxxxxxxxxxx>]

I suppose it comes from the old usage of canaries (the birds) in
mining. If noxious gases were present, and the canary died, then the
miners knew to exit quickly!

Live canary == good
Dead canary == bad

--gilbert

On 1/10/06, Ulf Lamping <ulf.lamping@xxxxxx> wrote:
> Jaap Keuter wrote:
>
> >It's a trick to put a specific value (the canary) at the top of the stack
> >frame or end of allocated buffer. When the stack frame of buffer is
> >released, the canary should still be there. If not the code has reached
> >too far up the stack or into the buffer, indicating an error.
> >
> >Check this paper on stackguard:
> >http://gcc.fyxm.net/summit/2003/Stackguard.pdf
> >
> >
> Ah, thanks for the explanation.
>
> I know this technique as adding a "gap" or "no mans land", never heard
> canary before :-)
>
> Regards, ULFL
>
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