[PATCH] drm: Make sure that encoder_type for drm_encoder_init() is in the list

[Daniel Vetter]

On Thu, Jun 21, 2018 at 05:04:02PM -0600, Jordan Crouse wrote:
> If a encoder name isn't specified for drm_encoder_init() it will try
> to construct one based on the incoming encoder_type identifier. If the
> caller passes an invalid encoder_type value the lookup could walk right
> past the end of the table.
> 
> Signed-off-by: Jordan Crouse <jcrouse at codeaurora.org>
> ---
>  drivers/gpu/drm/drm_encoder.c | 6 ++++++
>  1 file changed, 6 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_encoder.c b/drivers/gpu/drm/drm_encoder.c
> index 273e1c59c54a..4cf6c3bb8503 100644
> --- a/drivers/gpu/drm/drm_encoder.c
> +++ b/drivers/gpu/drm/drm_encoder.c
> @@ -128,6 +128,12 @@ int drm_encoder_init(struct drm_device *dev,
>  		encoder->name = kvasprintf(GFP_KERNEL, name, ap);
>  		va_end(ap);
>  	} else {
> +		/* Make sure that the requested encoder type is in the list */
> +		if (encoder_type >= ARRAY_SIZE(drm_encoder_enum_list)) {

I think moving that to the top and wrapping it in a WARN_ON would be even
better - specifying and invalid encoder type is clearly a driver bug.
-Daniel

> +			ret = -EINVAL;
> +			goto out_put;
> +		}
> +
>  		encoder->name = kasprintf(GFP_KERNEL, "%s-%d",
>  					  drm_encoder_enum_list[encoder_type].name,
>  					  encoder->base.id);
> -- 
> 2.17.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch