Re: cu coredumps

[Mark Cullen <mark.cullen@xxxxxxxxxxxxx>]

Adrian Nida wrote:
> > tmp_cp = malloc(sizeof(char) * 10);
> > cp = tmp_cp
> > free(tmp_cp);
> > tmp_cp = NULL;
> >
> > then cp would now be pointing to a block of memory that could be used by
> > some other process/overwritten? Would that not make it impossible for me
> > to actually free tmp_cp, as cp needs it?
>
>
> This frees the memory that tmp_cp && cp both *point to*. From that point on,
> if you reference cp you'll hopefully segfault because you're referencing
> garbage.  Worst case, someone will put some malicious code at that memory
> location and 0wn3 your box.

That's what I thought, but I thought when you called free() it didn't 
actually touch the data there, just mark it as free for other programs 
to use or something?

So.. it's actually pretty impossible for me to free tmp_cp anyway in 
this case isn't it? The function seems to return cp as an integer, so I 
can't free tmp_cp if I need cp pointing, so be able to prepend(?) /dev/ 
into the string?

Maybe there's some better way of doing it I guess. Maybe what I have 
done just isn't right anyway? :)

> Also if this is a local function, pointing tmp_cp to NULL does nothing
> useful except give you a clean stack.  That practice is most beneficial when
> using global/member variables. 
>
> Adrian


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