[Intel-gfx] [PATCH] drm: Declare that create drm_mm nodes with size 0 is illegal

[Daniel Vetter]

On Wed, Aug 03, 2016 at 07:26:28PM +0100, Chris Wilson wrote:
> At a higher level, all objects are created with definite size i.e. 0 is
> illegal. In forthcoming patches, this assumption is dependent upon in
> the drm_mm range manager, i.e. trying to create a drm_mm node with size
> 0 will have undefined behaviour. Add a couple of WARNs upon creating the
> drm_mm node to prevent later bugs.
> 
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>

Queued all up for -misc, will push out once -rc1 hits.
-Daniel

> ---
>  drivers/gpu/drm/drm_mm.c | 9 +++++++++
>  1 file changed, 9 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> index cb39f45d6a16..e8c15795386d 100644
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -185,6 +185,9 @@ int drm_mm_reserve_node(struct drm_mm *mm, struct drm_mm_node *node)
>  
>  	BUG_ON(node == NULL);
>  
> +	if (WARN_ON(node->size == 0))
> +		return -EINVAL;
> +
>  	end = node->start + node->size;
>  
>  	/* Find the relevant hole to add our node to */
> @@ -239,6 +242,9 @@ int drm_mm_insert_node_generic(struct drm_mm *mm, struct drm_mm_node *node,
>  {
>  	struct drm_mm_node *hole_node;
>  
> +	if (WARN_ON(size == 0))
> +		return -EINVAL;
> +
>  	hole_node = drm_mm_search_free_generic(mm, size, alignment,
>  					       color, sflags);
>  	if (!hole_node)
> @@ -340,6 +346,9 @@ int drm_mm_insert_node_in_range_generic(struct drm_mm *mm, struct drm_mm_node *n
>  {
>  	struct drm_mm_node *hole_node;
>  
> +	if (WARN_ON(size == 0))
> +		return -EINVAL;
> +
>  	hole_node = drm_mm_search_free_in_range_generic(mm,
>  							size, alignment, color,
>  							start, end, sflags);
> -- 
> 2.8.1
> 
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> Intel-gfx at lists.freedesktop.org
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch