[Mesa-dev] [PATCH] i965: miptree: prevent potential NULL pointer access

[Pohjolainen, Topi]

On Wed, Nov 09, 2016 at 04:38:43PM +0000, Lionel Landwerlin wrote:
> If the mcs buffer allocation fails we might get a NULL pointer. This
> was reported by Coverity and should only happen if we run out of
> memory.
> 
> CID: 1394290
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

Reviewed-by: Topi Pohjolainen <topi.pohjolainen at intel.com>

> ---
>  src/mesa/drivers/dri/i965/intel_mipmap_tree.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> index 6c81ffb..2115e09 100644
> --- a/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> +++ b/src/mesa/drivers/dri/i965/intel_mipmap_tree.c
> @@ -1486,6 +1486,8 @@ intel_miptree_init_mcs(struct brw_context *brw,
>                         struct intel_mipmap_tree *mt,
>                         int init_value)
>  {
> +   assert(mt->mcs_buf != NULL);
> +
>     /* From the Ivy Bridge PRM, Vol 2 Part 1 p326:
>      *
>      *     When MCS buffer is enabled and bound to MSRT, it is required that it
> @@ -1605,7 +1607,8 @@ intel_miptree_alloc_mcs(struct brw_context *brw,
>                                     mt->logical_height0,
>                                     MIPTREE_LAYOUT_ACCELERATED_UPLOAD);
>  
> -   intel_miptree_init_mcs(brw, mt, 0xFF);
> +   if (mt->mcs_buf)
> +      intel_miptree_init_mcs(brw, mt, 0xFF);
>  
>     return mt->mcs_buf != NULL;
>  }
> @@ -1671,7 +1674,7 @@ intel_miptree_alloc_non_msrt_mcs(struct brw_context *brw,
>      * used for lossless compression which requires similar initialisation
>      * as multi-sample compression.
>      */
> -   if (is_lossless_compressed) {
> +   if (mt->mcs_buf && is_lossless_compressed) {
>        /* Hardware sets the auxiliary buffer to all zeroes when it does full
>         * resolve. Initialize it accordingly in case the first renderer is
>         * cpu (or other none compression aware party).
> -- 
> 2.10.2
> 
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