[Mesa-dev] [PATCH 1/3] i965/drm: Fix dereference-before-NULL-check in brw_bo_unmap().

[Lionel Landwerlin]

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>

On 12/04/17 23:33, Kenneth Graunke wrote:
> I introduced this when cleaning up this code.  libdrm_intel was fine.
> While passing NULL to free() is a common pattern...passing NULL to
> unmap seems pretty bad.  You really ought to know whether you have
> a buffer or not.  So, we could add an assert.  Not sure whether
> that's better.  This takes the defensive plan of bailing early,
> which is what libdrm_intel did originally.
>
> CID: 1405006
> ---
>   src/mesa/drivers/dri/i965/brw_bufmgr.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_bufmgr.c b/src/mesa/drivers/dri/i965/brw_bufmgr.c
> index 8dda38d1262..fa7bf69a84e 100644
> --- a/src/mesa/drivers/dri/i965/brw_bufmgr.c
> +++ b/src/mesa/drivers/dri/i965/brw_bufmgr.c
> @@ -826,12 +826,12 @@ brw_bo_map_unsynchronized(struct brw_context *brw, struct brw_bo *bo)
>   int
>   brw_bo_unmap(struct brw_bo *bo)
>   {
> -   struct brw_bufmgr *bufmgr = bo->bufmgr;
> -   int ret = 0;
> -
>      if (bo == NULL)
>         return 0;
>   
> +   struct brw_bufmgr *bufmgr = bo->bufmgr;
> +   int ret = 0;
> +
>      pthread_mutex_lock(&bufmgr->lock);
>   
>      if (bo->map_count <= 0) {