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

[Jordan Crouse <jcrouse@codeaurora.org>]

On Fri, Jun 22, 2018 at 10:31:42AM +0200, Daniel Vetter wrote:
> 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@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

It wasn't immediately clear to me if it was legal to pass a "custom" encoder
type assuming you provided a name for it so I erred on the side of caution.
I would have no problem moving it up to the top and being loud about it.

Jordan

> > +			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
> > 
> > _______________________________________________
> > dri-devel mailing list
> > dri-devel@lists.freedesktop.org
> > https://lists.freedesktop.org/mailman/listinfo/dri-devel
> 
> -- 
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

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