linux-kernel - Re: [Spice-devel] [PATCH 1/3] drm/qxl: add mode/framebuffer check functions

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Date:   Wed, 16 Jan 2019 04:24:51 -0500 (EST)
From:   Frediano Ziglio <fziglio@...hat.com>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     dri-devel@...ts.freedesktop.org, David Airlie <airlied@...ux.ie>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <virtualization@...ts.linux-foundation.org>,
        Daniel Vetter <daniel@...ll.ch>,
        "open list:DRM DRIVER FOR QXL VIRTUAL GPU" 
        <spice-devel@...ts.freedesktop.org>,
        Dave Airlie <airlied@...hat.com>
Subject: Re: [Spice-devel] [PATCH 1/3] drm/qxl: add mode/framebuffer check
 functions

> 
> Add a helper functions to check video modes.  Also add a helper to check
> framebuffer buffer objects, using the former for consistency.  That way
> we should not fail in qxl_primary_atomic_check() because video modes
> which are too big will not be added to the mode list in the first place.
> 
> Signed-off-by: Gerd Hoffmann <kraxel@...hat.com>
> ---
>  drivers/gpu/drm/qxl/qxl_display.c | 37 +++++++++++++++++++------------------
>  1 file changed, 19 insertions(+), 18 deletions(-)
> 
> diff --git a/drivers/gpu/drm/qxl/qxl_display.c
> b/drivers/gpu/drm/qxl/qxl_display.c
> index 1f8fddcc34..07a37d52c4 100644
> --- a/drivers/gpu/drm/qxl/qxl_display.c
> +++ b/drivers/gpu/drm/qxl/qxl_display.c
> @@ -191,6 +191,21 @@ void qxl_display_read_client_monitors_config(struct
> qxl_device *qdev)
>  	}
>  }
>  
> +static int qxl_check_mode(struct qxl_device *qdev,
> +			  unsigned int width,
> +			  unsigned int height)
> +{
> +	if (width * height * 4 > qdev->vram_size)

Is someone checking for integer overflows already?

> +		return -ENOMEM;
> +	return 0;
> +}
> +
> +static int qxl_check_framebuffer(struct qxl_device *qdev,
> +				 struct qxl_bo *bo)
> +{
> +	return qxl_check_mode(qdev, bo->surf.width, bo->surf.height);
> +}
> +
>  static int qxl_add_monitors_config_modes(struct drm_connector *connector,
>                                           unsigned *pwidth,
>                                           unsigned *pheight)
> @@ -466,12 +481,7 @@ static int qxl_primary_atomic_check(struct drm_plane
> *plane,
>  
>  	bo = gem_to_qxl_bo(state->fb->obj[0]);
>  
> -	if (bo->surf.stride * bo->surf.height > qdev->vram_size) {
> -		DRM_ERROR("Mode doesn't fit in vram size (vgamem)");
> -		return -EINVAL;
> -	}
> -
> -	return 0;
> +	return qxl_check_framebuffer(qdev, bo);
>  }
>  
>  static int qxl_primary_apply_cursor(struct drm_plane *plane)
> @@ -941,20 +951,11 @@ static enum drm_mode_status qxl_conn_mode_valid(struct
> drm_connector *connector,
>  {
>  	struct drm_device *ddev = connector->dev;
>  	struct qxl_device *qdev = ddev->dev_private;
> -	int i;
>  
> -	/* TODO: is this called for user defined modes? (xrandr --add-mode)
> -	 * TODO: check that the mode fits in the framebuffer */
> +	if (qxl_check_mode(qdev, mode->hdisplay, mode->vdisplay) != 0)
> +		return MODE_BAD;
>  
> -	if (qdev->monitors_config_width == mode->hdisplay &&
> -	    qdev->monitors_config_height == mode->vdisplay)
> -		return MODE_OK;
> -
> -	for (i = 0; i < ARRAY_SIZE(common_modes); i++) {
> -		if (common_modes[i].w == mode->hdisplay && common_modes[i].h ==
> mode->vdisplay)
> -			return MODE_OK;
> -	}
> -	return MODE_BAD;
> +	return MODE_OK;
>  }
>  
>  static struct drm_encoder *qxl_best_encoder(struct drm_connector *connector)

Frediano