[Mesa-dev] Fix a crash in update_texture_state() when requesting a fallback for external texture target

[Brian Paul]

On 10/10/2012 05:42 AM, Abdiel Janulgue wrote:
> I found a crash where updating the texture unit states ends up requesting a
> fallback texture for a  GL_TEXTURE_EXTERNAL_OES target and sets a null current
> texture object for the current unit.
>
> This is a fix by supporting  TEXTURE_EXTERNAL_INDEX target in
> _mesa_get_fallback_texture() and making sure the texture unit is not really
> used should an invalid  fallback be returned.
>
> Cheers,
> -abdiel
>
> diff --git a/src/mesa/main/texobj.c b/src/mesa/main/texobj.c
> index e0494c9..7e2b6b5 100644
> --- a/src/mesa/main/texobj.c
> +++ b/src/mesa/main/texobj.c
> @@ -771,6 +771,9 @@ _mesa_get_fallback_texture(struct gl_context *ctx,
> gl_texture_index tex)
>            target = GL_TEXTURE_BUFFER;
>            break;
>         case TEXTURE_EXTERNAL_INDEX:
> +         dims = 2;
> +         target = GL_TEXTURE_EXTERNAL_OES;
> +         break;
>         default:
>            /* no-op */
>            return NULL;
> diff --git a/src/mesa/main/texstate.c b/src/mesa/main/texstate.c
> index 8ca9092..009b077 100644
> --- a/src/mesa/main/texstate.c
> +++ b/src/mesa/main/texstate.c
> @@ -600,6 +600,11 @@ update_texture_state( struct gl_context *ctx )
>
>               texTarget = (gl_texture_index) (ffs(enabledTargets) - 1);
>               texObj = _mesa_get_fallback_texture(ctx, texTarget);
> +
> +            if (!texObj)
> +               /* invalid fallback texture: make sure to disable texture unit
> */
> +               continue;

So texObj should only be null here if _mesa_get_fallback_texture() 
fails because of a bad/unsupported texture target or we run out of 
memory for a 1-texel texture (pretty unlikely).

So I think I'd like to see an assert(texObj) there followed by the 
if/continue so that we get the assertion with debug builds but don't 
crash with release builds.

Looks OK otherwise.

> +
>               _mesa_reference_texobj(&texUnit->_Current, texObj);
>               texUnit->_ReallyEnabled = 1<<  texTarget;
>            }
>

-Brian