[PATCH libX11 2/3] XKB: Avoid a possible NULL dereference

[Jeremy Huddleston]

This is the one that I especially wanted to review on the list because it doesn't sit well with me.

Hitting the default switch-case in the first run through the loop results in a NULL dereference (rbounds) when calling _XkbCheckBounds.  In subsequent runs, we get lucky in that rbounds was set in an earlier iteration through the loop.  I'm not really familiar enough with XKB to know what is going on here.

Should we be doing this:
rbounds= &tbounds;

or should we just be skipping the check (which is what I accidentally pushed)?

http://people.freedesktop.org/~jeremyhu/analyzer/yuffie/20110504-0000/libX11/report-F0RlNS.html#EndPath

On May 4, 2011, at 11:50, Jeremy Huddleston wrote:

> 
> XKBGeom.c:191:25: warning: Access to field 'x1' results in a dereference of a null pointer (loaded from variable 'rbounds')
>        _XkbCheckBounds(bounds,rbounds->x1,rbounds->y1);
>                               ^~~~~~~
> 
> Found-by: clang static analyzer
> Signed-off-by: Jeremy Huddleston <jeremyhu at apple.com>
> ---
> src/xkb/XKBGeom.c |    4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/src/xkb/XKBGeom.c b/src/xkb/XKBGeom.c
> index e9e36d0..2365f48 100644
> --- a/src/xkb/XKBGeom.c
> +++ b/src/xkb/XKBGeom.c
> @@ -147,7 +147,7 @@ register int	i;
> XkbShapePtr	shape;
> XkbRowPtr	row;
> XkbDoodadPtr	doodad;
> -XkbBoundsPtr	bounds,rbounds=NULL;
> +XkbBoundsPtr	bounds,rbounds;
> 
>     if ((!geom)||(!section))
> 	return False;
> @@ -186,7 +186,7 @@ XkbBoundsPtr	bounds,rbounds=NULL;
> 	    default:
> 		tbounds.x1= tbounds.x2= doodad->any.left;
> 		tbounds.y1= tbounds.y2= doodad->any.top;
> -		break;
> +		continue;
> 	}
> 	_XkbCheckBounds(bounds,rbounds->x1,rbounds->y1);
> 	_XkbCheckBounds(bounds,rbounds->x2,rbounds->y2);
> -- 
> 1.7.4.1
> 
> 
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