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List:       mesa3d-dev
Subject:    Re: [Mesa3d-dev] Mesa (mesa_7_7_branch): st/xorg: Prevent potential
From:       Michel =?ISO-8859-1?Q?D=E4nzer?= <michel () daenzer ! net>
Date:       2009-11-23 12:49:40
Message-ID: 1258980580.20259.898.camel () thor ! local
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On Sat, 2009-11-21 at 22:11 -0800, Vinson Lee wrote: 
> Module: Mesa
> Branch: mesa_7_7_branch
> Commit: 88aab56a26dd33a2d3177a41420f00473d7270af
> URL:    http://cgit.freedesktop.org/mesa/mesa/commit/?id=88aab56a26dd33a2d3177a41420f00473d7270af
> 
> Author: Vinson Lee <vlee@vmware.com>
> Date:   Sun Nov 22 01:10:38 2009 -0500
> 
> st/xorg: Prevent potential null pointer deference in xorg_xv.c.
> 
> ---
> 
>  src/gallium/state_trackers/xorg/xorg_xv.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/src/gallium/state_trackers/xorg/xorg_xv.c b/src/gallium/state_trackers/xorg/xorg_xv.c
> index a1e74fa..e7f4900 100644
> --- a/src/gallium/state_trackers/xorg/xorg_xv.c
> +++ b/src/gallium/state_trackers/xorg/xorg_xv.c
> @@ -446,7 +446,7 @@ display_video(ScrnInfoPtr pScrn, struct xorg_xv_port_priv *pPriv, int id,
>     int x, y, w, h;
>     struct exa_pixmap_priv *dst = exaGetPixmapDriverPrivate(pPixmap);
>  
> -   if (!dst->tex) {
> +   if (dst && !dst->tex) {
>  	xorg_exa_set_shared_usage(pPixmap);
>  	pScrn->pScreen->ModifyPixmapHeader(pPixmap, 0, 0, 0, 0, 0, NULL);
>     }

This is not a good fix; the same dance as for the !tex case in
xorg_dri2.c:driDoCreateBuffer() would be necessary to ensure that
there's a pixmap driver private and a texture. I consciously left that
out because I couldn't seem to find any case where the driver private
doesn't exist. If such cases do indeed exist, I'd rather get a clean
crash than more subtle failure.

In general, one must be careful not to just paper over theoretical
issues pointed out by automated tools.


-- 
Earthling Michel Dänzer           |                http://www.vmware.com
Libre software enthusiast         |          Debian, X and DRI developer

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