Re: [PATCH -fixes] vmwgfx: fix incorrect VRAM size check in vmw_kms_fb_create()

[Thomas Hellstrom <thellstrom@vmware.com>]

This looks good, although I want to do a quick test to verify that it 
doesn't break anything.

I'll get back as soon as possible.

/Thomas

On 12/21/2011 11:18 AM, Xi Wang wrote:
> Commit e133e737 didn't correctly fix the integer overflow issue.
>
> -	unsigned int required_size;
> +	u64 required_size;
> 	...
> 	required_size = mode_cmd->pitch * mode_cmd->height;
> -	if (unlikely(required_size>  dev_priv->vram_size)) {
> +	if (unlikely(required_size>  (u64) dev_priv->vram_size)) {
>
> Note that both pitch and height are u32.  Their product is still u32 and
> would overflow before being assigned to required_size.  A correct way is
> to convert pitch and height to u64 before the multiplication.
>
> 	required_size = (u64)mode_cmd->pitch * (u64)mode_cmd->height;
>
> This patch calls the existing vmw_kms_validate_mode_vram() for
> validation.
>
> Signed-off-by: Xi Wang<xi.wang@gmail.com>
> ---
>   drivers/gpu/drm/vmwgfx/vmwgfx_kms.c |    6 +++---
>   1 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> index 8aa1dbb..f94b33a 100644
> --- a/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_kms.c
> @@ -1093,7 +1093,6 @@ static struct drm_framebuffer *vmw_kms_fb_create(struct drm_device *dev,
>   	struct vmw_surface *surface = NULL;
>   	struct vmw_dma_buffer *bo = NULL;
>   	struct ttm_base_object *user_obj;
> -	u64 required_size;
>   	int ret;
>
>   	/**
> @@ -1102,8 +1101,9 @@ static struct drm_framebuffer *vmw_kms_fb_create(struct drm_device *dev,
>   	 * requested framebuffer.
>   	 */
>
> -	required_size = mode_cmd->pitch * mode_cmd->height;
> -	if (unlikely(required_size>  (u64) dev_priv->vram_size)) {
> +	if (!vmw_kms_validate_mode_vram(dev_priv,
> +					mode_cmd->pitch,
> +					mode_cmd->height)) {
>   		DRM_ERROR("VRAM size is too small for requested mode.\n");
>   		return ERR_PTR(-ENOMEM);
>   	}
>