Re: [PATCH] drm/msm: Fix return type of mdp4_lvds_connector_mode_valid

[Dmitry Baryshkov]

On 01/11/2022 01:10, Nathan Chancellor wrote:
> On Tue, Sep 13, 2022 at 01:55:48PM -0700, Nathan Huckleberry wrote:
> > The mode_valid field in drm_connector_helper_funcs is expected to be of
> > type:
> > enum drm_mode_status (* mode_valid) (struct drm_connector *connector,
> >                                       struct drm_display_mode *mode);
> >
> > The mismatched return type breaks forward edge kCFI since the underlying
> > function definition does not match the function hook definition.
> >
> > The return type of mdp4_lvds_connector_mode_valid should be changed from
> > int to enum drm_mode_status.
> >
> > Reported-by: Dan Carpenter <error27@xxxxxxxxx>
> > Link: https://github.com/ClangBuiltLinux/linux/issues/1703
> > Cc: llvm@xxxxxxxxxxxxxxx
> > Signed-off-by: Nathan Huckleberry <nhuck@xxxxxxxxxx>
> > ---
> >   drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c | 5 +++--
> >   1 file changed, 3 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
> > index 7288041dd86a..7444b75c4215 100644
> > --- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
> > +++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c
> > @@ -56,8 +56,9 @@ static int mdp4_lvds_connector_get_modes(struct drm_connector *connector)
> >   	return ret;
> >   }
> >   
> > -static int mdp4_lvds_connector_mode_valid(struct drm_connector *connector,
> > -				 struct drm_display_mode *mode)
> > +static enum drm_mode_status
> > +mdp4_lvds_connector_mode_valid(struct drm_connector *connector,
> > +			       struct drm_display_mode *mode)
> >   {
> >   	struct mdp4_lvds_connector *mdp4_lvds_connector =
> >   			to_mdp4_lvds_connector(connector);
> > --
> > 2.37.2.789.g6183377224-goog
>
> Did this patch get lost somewhere? I do not see it picked up. It is
> needed to avoid a new WIP warning from clang for catching these CFI
> failures:
>
> drivers/gpu/drm/msm/disp/mdp4/mdp4_lvds_connector.c:89:16: error: incompatible function pointer types initializing 'enum drm_mode_status (*)(struct drm_connector *, struct drm_display_mode *)' with an expression of type 'int (struct drm_connector *, struct drm_display_mode *)' [-Werror,-Wincompatible-function-pointer-types-strict]
>          .mode_valid = mdp4_lvds_connector_mode_valid,
>                        ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 1 error generated.

It will be picked into 6.1-rc and then propagate through the stable 
kernel updates.

Anyway:

Fixes: 3e87599b68e7 ("drm/msm/mdp4: add LVDS panel support")
Reviewed-by: Dmitry Baryshkov <dmitry.baryshkov@xxxxxxxxxx>


--
With best wishes
Dmitry