Re: [PATCH] drm/i915: check vma for error in ggtt_unpin_view

From: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
To: Matthew Auld <matthew.auld@intel.com>, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH] drm/i915: check vma for error in ggtt_unpin_view
Date: Thu, 24 Mar 2016 16:32:57 +0200	[thread overview]
Message-ID: <1458829977.7860.17.camel@linux.intel.com> (raw)
In-Reply-To: <1458747584-29772-1-git-send-email-matthew.auld@intel.com>

On ke, 2016-03-23 at 15:39 +0000, Matthew Auld wrote:
> When unpinning a ggtt_view check vma for error, otherwise we may end up
> accessing an invalid pointer.
> 
> Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
> Signed-off-by: Matthew Auld <matthew.auld@intel.com>
> ---
>  drivers/gpu/drm/i915/i915_gem.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 8588c83..a8f3378 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -4319,7 +4319,7 @@ i915_gem_object_ggtt_unpin_view(struct drm_i915_gem_object *obj,
>  {
>  	struct i915_vma *vma = i915_gem_obj_to_ggtt_view(obj, view);
>  
> -	BUG_ON(!vma);
> +	BUG_ON(IS_ERR_OR_NULL(vma));

Nicely spotted.

I discussed this with Tvrtko (CC'd him). I think we could
change i915_gem_obj_to_ggtt_view to BUG_ON(!view) instead of adding the
error handling in all places, as it is after all a programmer error to
provide NULL view.

Regards, Joonas

>  	WARN_ON(vma->pin_count == 0);
>  	WARN_ON(!i915_gem_obj_ggtt_bound_view(obj, view));
>  
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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