Re: [PATCH] drm/i915/display: Check source height is > 0

["Ville Syrjälä" <ville.syrjala@linux.intel.com>]

On Mon, Dec 26, 2022 at 10:53:24PM -0700, Drew Davenport wrote:
> The error message suggests that the height of the src rect must be at
> least 1. Reject source with height of 0.
> 
> Signed-off-by: Drew Davenport <ddavenport@chromium.org>
> 
> ---
> I was investigating some divide-by-zero crash reports on ChromeOS which
> pointed to the intel_adjusted_rate function. Further prodding showed
> that I could reproduce this in a simple test program if I made src_h
> some value less than 1 but greater than 0.
> 
> This seemed to be a sensible place to check that the source height is at
> least 1. I tried to repro this issue on an amd device I had on hand, and
> the configuration was rejected.
> 
> Would it make sense to add a check that source dimensions are at least 1
> somewhere in core, like in drm_atomic_plane_check? Or is that a valid
> use case on some devices, and thus any such check should be done on a
> per-driver basis?
> 
> Thanks.
> 
>  drivers/gpu/drm/i915/display/skl_universal_plane.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/display/skl_universal_plane.c b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> index 4b79c2d2d6177..9b172a1e90deb 100644
> --- a/drivers/gpu/drm/i915/display/skl_universal_plane.c
> +++ b/drivers/gpu/drm/i915/display/skl_universal_plane.c
> @@ -1627,7 +1627,7 @@ static int skl_check_main_surface(struct intel_plane_state *plane_state)
>  	u32 offset;
>  	int ret;
>  
> -	if (w > max_width || w < min_width || h > max_height) {
> +	if (w > max_width || w < min_width || h > max_height || h < 1) {

I liked this one best so pushed to drm-intel-next with cc:stable. Thanks.

In the future we might want to move some of these checks to an earlier
spot to make sure we don't hit any other weird issues in some other
code, but for the moment I think this will do.

>  		drm_dbg_kms(&dev_priv->drm,
>  			    "requested Y/RGB source size %dx%d outside limits (min: %dx1 max: %dx%d)\n",
>  			    w, h, min_width, max_width, max_height);
> -- 
> 2.39.0.314.g84b9a713c41-goog

-- 
Ville Syrjälä
Intel