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

[Ulf Lamping <ulf.lamping@xxxxxx>]

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