Re: [PATCH v2] drm: Warn if plane/crtc/encoder/connector index exceeds our 32bit bitmasks

[Maarten Lankhorst <maarten.lankhorst@linux.intel.com>]

Op 24-01-18 om 22:47 schreef Ville Syrjala:
> From: Ville Syrjälä <ville.syrjala@linux.intel.com>
>
> We use 32bit bitmasks to track planes/crtcs/encoders/connectors.
> Naturally we can only do that if the index of those objects stays
> below 32. Issue a warning whenever we exceed that limit, hopefully
> prompting someone to fix the problem.
>
> For connectors the issue is a bit more complicated as they can
> be created/destroyed at runtime due to MST. So the problem is no
> longer a purely theoretical programmer error. As the connector
> indexes are allocated via ida, we can simply limit the maximum
> value the ida is allowed to hand out. The error handling is already
> in place.
>
> v2: Return an error to the caller (Harry)
>
> Cc: Harry Wentland <harry.wentland@amd.com>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
> Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/drm_connector.c | 3 ++-
>  drivers/gpu/drm/drm_crtc.c      | 4 ++++
>  drivers/gpu/drm/drm_encoder.c   | 4 ++++
>  drivers/gpu/drm/drm_plane.c     | 4 ++++
>  4 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index b85a7749709d..f4a689ab990a 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -205,7 +205,8 @@ int drm_connector_init(struct drm_device *dev,
>  	connector->dev = dev;
>  	connector->funcs = funcs;
>  
> -	ret = ida_simple_get(&config->connector_ida, 0, 0, GFP_KERNEL);
> +	/* connector index is used with 32bit bitmasks */
> +	ret = ida_simple_get(&config->connector_ida, 0, 32, GFP_KERNEL);
>  	if (ret < 0)
>  		goto out_put;
>  	connector->index = ret;
Could we also put a DRM_DEBUG_KMS in here if allocation fails? Since it's more likely to happen now..

Otherwise looks good so with that change:
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
> index f0556e654116..5b4be382a1d7 100644
> --- a/drivers/gpu/drm/drm_crtc.c
> +++ b/drivers/gpu/drm/drm_crtc.c
> @@ -282,6 +282,10 @@ int drm_crtc_init_with_planes(struct drm_device *dev, struct drm_crtc *crtc,
>  	WARN_ON(primary && primary->type != DRM_PLANE_TYPE_PRIMARY);
>  	WARN_ON(cursor && cursor->type != DRM_PLANE_TYPE_CURSOR);
>  
> +	/* crtc index is used with 32bit bitmasks */
> +	if (WARN_ON(config->num_crtc >= 32))
> +		return -EINVAL;
> +
>  	crtc->dev = dev;
>  	crtc->funcs = funcs;
>  
> diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
> index 59e0ebe733f8..273e1c59c54a 100644
> --- a/drivers/gpu/drm/drm_encoder.c
> +++ b/drivers/gpu/drm/drm_encoder.c
> @@ -110,6 +110,10 @@ int drm_encoder_init(struct drm_device *dev,
>  {
>  	int ret;
>  
> +	/* encoder index is used with 32bit bitmasks */
> +	if (WARN_ON(dev->mode_config.num_encoder >= 32))
> +		return -EINVAL;
> +
>  	ret = drm_mode_object_add(dev, &encoder->base, DRM_MODE_OBJECT_ENCODER);
>  	if (ret)
>  		return ret;
> diff --git a/drivers/gpu/drm/drm_plane.c b/drivers/gpu/drm/drm_plane.c
> index 2c90519576a3..22b54663b6e7 100644
> --- a/drivers/gpu/drm/drm_plane.c
> +++ b/drivers/gpu/drm/drm_plane.c
> @@ -173,6 +173,10 @@ int drm_universal_plane_init(struct drm_device *dev, struct drm_plane *plane,
>  	unsigned int format_modifier_count = 0;
>  	int ret;
>  
> +	/* plane index is used with 32bit bitmasks */
> +	if (WARN_ON(config->num_total_plane >= 32))
> +		return -EINVAL;
> +
>  	ret = drm_mode_object_add(dev, &plane->base, DRM_MODE_OBJECT_PLANE);
>  	if (ret)
>  		return ret;


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