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

[Abdiel Janulgue]

On Wednesday, October 10, 2012 08:33:08 AM Brian Paul wrote:
> 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.

Thanks Brian. I've pushed the improved changes with your feedback to 
git at gitorious.org:mesa3d/mesa.git master branch

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