Re: Buffer Overflow

From: Absolute Newbie (absnewbie@hotmail.com)
Date: 04/06/03 

From: absnewbie@hotmail.com (Absolute Newbie)
Date: 5 Apr 2003 17:20:47 -0800

Juha Laiho <Juha.Laiho@iki.fi> wrote:
-------------------------------------
> I've been bitten by this - and there is a need to zero the buffer you get
> from malloc(): while the OS memory allocation routines will clear (to
> some value; I think the actual value hasn't been specified) the memory
> areas they're giving to your process, malloc() may also return memory
> that was already used by your process, but free()'d (but still not yet
> returned to the OS). And in this case the contents will not be scrubbed;
> the memory will contain whatever it did contain when your program freed
> the area.

A simple way to avoid unpredicted results is to always use calloc()
instead of malloc(). calloc() will zero out the buffer upon
allocation:

char *buffer = calloc(1024, 1);

instead of:

char *buffer = malloc(1024);
memset(buffer, 0, 1024); /* you could forget this one :) */

regards,

absnewbie

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