linux-kernel - Re: [PATCH] drm/mm: avoid possible null pointer dereference

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Date:	Mon, 23 May 2016 11:27:14 +0100
From:	Eric Engestrom <eric.engestrom@...tec.com>
To:	Heinrich Schuchardt <xypron.glpk@....de>
CC:	David Airlie <airlied@...ux.ie>, <linux-kernel@...r.kernel.org>,
	<dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH] drm/mm: avoid possible null pointer dereference

On Wed, May 18, 2016 at 10:17:19PM +0200, Heinrich Schuchardt wrote:
> Do not dereference node before the check if node is NULL.
> 
> Signed-off-by: Heinrich Schuchardt <xypron.glpk@....de>
> ---
>  drivers/gpu/drm/drm_mm.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c
> index 04de6fd..cb39f45 100644
> --- a/drivers/gpu/drm/drm_mm.c
> +++ b/drivers/gpu/drm/drm_mm.c
> @@ -179,12 +179,14 @@ static void drm_mm_insert_helper(struct drm_mm_node *hole_node,
>  int drm_mm_reserve_node(struct drm_mm *mm, struct drm_mm_node *node)
>  {
>  	struct drm_mm_node *hole;
> -	u64 end = node->start + node->size;
> +	u64 end;
>  	u64 hole_start;
>  	u64 hole_end;
>  
>  	BUG_ON(node == NULL);
>  
> +	end = node->start + node->size;
> +
>  	/* Find the relevant hole to add our node to */
>  	drm_mm_for_each_hole(hole, mm, hole_start, hole_end) {
>  		if (hole_start > node->start || hole_end < end)
> -- 
> 2.1.4

Reviewed-by: Eric Engestrom <eric.engestrom@...tec.com>