[Mesa-dev] [PATCH 02/27] i965/miptree: Remove redundant check for null texture

[Pohjolainen, Topi]

On Mon, Jan 16, 2017 at 08:33:09AM -0800, Jason Ekstrand wrote:
>    On Mon, Jan 16, 2017 at 1:13 AM, Topi Pohjolainen
>    <[1]topi.pohjolainen at gmail.com> wrote:
> 
>      There exact same check earlier in brw_miptree_layout() which
>      intel_miptree_create_layout() in turn calls unconditionally.
>      Signed-off-by: Topi Pohjolainen <[2]topi.pohjolainen at intel.com>
>      ---
>       src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 7 +------
>       1 file changed, 1 insertion(+), 6 deletions(-)
>      diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
>      b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
>      index 25f8f39..9488bec 100644
>      --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
>      +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
>      @@ -628,13 +628,8 @@ miptree_create(struct brw_context *brw,
>                                           first_level, last_level,
>      width0,
>                                           height0, depth0, num_samples,
>                                           layout_flags);
>      -   /*
>      -    * pitch == 0 || height == 0  indicates the null texture
>      -    */
>      -   if (!mt || !mt->total_width || !mt->total_height) {
>      -      intel_miptree_release(&mt);
>      +   if (!mt)
>             return NULL;
> 
>    Ugh... Not quite.  More miptree nastiness!  Looking through the code,
>    brw_miptree_layout does do this check and unrefs the miptree but has no
>    way of indicating to higher levels that it has unref'd the miptree!  In
>    other words, if that ever happens, the aux_disable lines at the end of
>    intel_miptree_create_layout will read/write freed memory and
>    intel_miptree_create_layout will a valid-looking (but freed) pointer.

Indeed, good catch!!

I sent an additional patch that propagates the error. This patch should be
safe on top of that.

> 
>      -   }
>          if (mt->tiling == (I915_TILING_Y | I915_TILING_X))
>             mt->tiling = I915_TILING_Y;
>      --
>      2.5.5
>      _______________________________________________
>      mesa-dev mailing list
>      [3]mesa-dev at lists.freedesktop.org
>      [4]https://lists.freedesktop.org/mailman/listinfo/mesa-dev
> 
> References
> 
>    1. mailto:topi.pohjolainen at gmail.com
>    2. mailto:topi.pohjolainen at intel.com
>    3. mailto:mesa-dev at lists.freedesktop.org
>    4. https://lists.freedesktop.org/mailman/listinfo/mesa-dev