Re: Suggestion on "int len" sanity

[Geert Uytterhoeven]

On Wed, 1 Jun 2005, Willy Tarreau wrote:
> On Wed, Jun 01, 2005 at 09:06:33AM +0200, XIAO Gang wrote:
> > I would like to make a security suggestion.
> > 
> > There are many length variables in the kernel, locally declared as "len" 
> > or "length", either as "int", "unsigned int" or "size_t". However, 
> > declaring a length as "int" leads easily to an erroneous situation, as 
> > the author (or even a code checker) might make the implicite hypothesis 
> > that the length is positive, so that it is enough to make a sanity check 
> > of the kind
> > 
> > if (length > limit) ERROR;
> > 
> > which is not enough.
> > 
> > On the other hand, when a variable is named "len" or "length", it is 
> > usually used for length and never should go negative. So could I suggest 
> > that the declarations of these variables to be uniformized to "size_t", 
> > via a gradual but sysmatic cleanup?
> 
> Probably true for most cases, but be careful of code which would use
> -1 to report some errors if such thing exists.

In that case, use ssize_t.

Gr{oetje,eeting}s,

						Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds
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