Re: [PATCH] drm/msm/mdp4: Fix refcount leak in mdp4_modeset_init_intf

[Dmitry Baryshkov]

On 14/06/2022 13:07, Miaoqian Lin wrote:
> Hi, Abhinav
>
> On 2022/6/11 7:20, Abhinav Kumar wrote:
> > On 6/7/2022 4:08 AM, Miaoqian Lin wrote:
> > > of_graph_get_remote_node() returns remote device node pointer with
> > > refcount incremented, we should use of_node_put() on it
> > > when not need anymore.
> > > Add missing of_node_put() to avoid refcount leak.
> > >
> > > Fixes: 86418f90a4c1 ("drm: convert drivers to use of_graph_get_remote_node")
> > > Signed-off-by: Miaoqian Lin <linmq006@xxxxxxxxx>
> > > ---
> > >    drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c | 2 ++
> > >    1 file changed, 2 insertions(+)
> >
> > This patch itself looks fine and will cover the cases when there was an error and we did not release the refcount.
> >
> > But, even in the normal cases I am not finding where we are releasing the refcount for the panel_node.
> >
> > I dont see a of_node_put() on mdp4_lcdc_encoder->panel_node.
> Thanks for your review.
>
> I don't see it either. It's a bit messy because the reference assigned to mdp4_lcdc_encoder->panel_node and mdp4_lvds_connector->panel_node both.

I have a plan to rework mdp4 lcdc support once I get my ifc6410 lvds 
cable. Thus I think we can land this patch now and fix the mdp4 
lcdc/lvds code leaking the reference in the due time.

> > Am i missing something?
> >
> > > diff --git a/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c b/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c
> > > index fb48c8c19ec3..17cb1fc78379 100644
> > > --- a/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c
> > > +++ b/drivers/gpu/drm/msm/disp/mdp4/mdp4_kms.c
> > > @@ -216,6 +216,7 @@ static int mdp4_modeset_init_intf(struct mdp4_kms *mdp4_kms,
> > >            encoder = mdp4_lcdc_encoder_init(dev, panel_node);
> > >            if (IS_ERR(encoder)) {
> > >                DRM_DEV_ERROR(dev->dev, "failed to construct LCDC encoder\n");
> > > +            of_node_put(panel_node);
> > >                return PTR_ERR(encoder);
> > >            }
> > >    @@ -225,6 +226,7 @@ static int mdp4_modeset_init_intf(struct mdp4_kms *mdp4_kms,
> > >            connector = mdp4_lvds_connector_init(dev, panel_node, encoder);
> > >            if (IS_ERR(connector)) {
> > >                DRM_DEV_ERROR(dev->dev, "failed to initialize LVDS connector\n");
> > > +            of_node_put(panel_node);
> > >                return PTR_ERR(connector);
> > >            }
> > >    


--
With best wishes
Dmitry