Re: [PATCH 6/7] drm/rcar: gem: dumb: pitch is an output

[Daniel Vetter <daniel@ffwll.ch>]

On Wed, Nov 05, 2014 at 02:25:18PM +0100, Thierry Reding wrote:
> From: Thierry Reding <treding@nvidia.com>
> 
> When creating a dumb buffer object using the DRM_IOCTL_MODE_CREATE_DUMB
> IOCTL, only the width, height, bpp and flags fields are inputs. The
> caller is not guaranteed to zero out or set handle, pitch and size.
> Drivers must not treat these values as possible inputs, otherwise they
> may use uninitialized memory during the computation of the framebuffer
> size.
> 
> The R-Car DU driver treats the pitch passed in from userspace as minimum
> and will only overwrite it when the driver-computed pitch is larger,
> allowing userspace to, intentionally or not, overallocate framebuffers.
> 
> Signed-off-by: Thierry Reding <treding@nvidia.com>

Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

Aside: I tend to put the maintainer Cc: into the patch so that they're on
the permanent record. That will also make sure that when this patch gets
resend (e.g. stable backport) maintainers are still included properly.
-Daniel

> ---
>  drivers/gpu/drm/rcar-du/rcar_du_kms.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/rcar-du/rcar_du_kms.c b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> index 5329491e32c3..6289e3797bc5 100644
> --- a/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> +++ b/drivers/gpu/drm/rcar-du/rcar_du_kms.c
> @@ -126,7 +126,7 @@ int rcar_du_dumb_create(struct drm_file *file, struct drm_device *dev,
>  	else
>  		align = 16 * args->bpp / 8;
>  
> -	args->pitch = roundup(max(args->pitch, min_pitch), align);
> +	args->pitch = roundup(min_pitch, align);
>  
>  	return drm_gem_cma_dumb_create_internal(file, dev, args);
>  }
> -- 
> 2.1.3
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch
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