Re: [PATCH] drm: sti: fix device leaks at component probe

Johan Hovold
2025-11-04T11:21:24Z

On Fri, Oct 31, 2025 at 06:10:46PM +0100, Raphaël Gallais-Pou wrote:

> Le Mon, Sep 22, 2025 at 02:20:12PM +0200, Johan Hovold a écrit :
> > Make sure to drop the references taken to the vtg devices by
> > of_find_device_by_node() when looking up their driver data during
> > component probe.
>
> Markus suggested “Prevent device leak in of_vtg_find()” as commit
> summary.

Markus has gotten himself banned from the mailing lists some years ago
and even if he is now back with a new mail address most of us still
ignore him.

I prefer the Subject as it stands since it captures when the leaks
happens, but I don't mind mentioning of_vtg_find() instead if you
insist.

> > Note that holding a reference to a platform device does not prevent its
> > driver data from going away so there is no point in keeping the
> > reference after the lookup helper returns.
> >
> > Fixes: cc6b741c6f63 ("drm: sti: remove useless fields from vtg structure")
> > Cc: stable@vger.kernel.org # 4.16
> > Cc: Benjamin Gaignard <benjamin.gaignard@collabora.com>
> > Signed-off-by: Johan Hovold <johan@kernel.org>
> > ---
> > drivers/gpu/drm/sti/sti_vtg.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/sti/sti_vtg.c b/drivers/gpu/drm/sti/sti_vtg.c
> > index ee81691b3203..ce6bc7e7b135 100644
> > --- a/drivers/gpu/drm/sti/sti_vtg.c
> > +++ b/drivers/gpu/drm/sti/sti_vtg.c
> > @@ -143,12 +143,17 @@ struct sti_vtg {
> > struct sti_vtg *of_vtg_find(struct device_node *np)
> > {
> > struct platform_device *pdev;
> > + struct sti_vtg *vtg;
> >
> > pdev = of_find_device_by_node(np);
> > if (!pdev)
> > return NULL;
> >
> > - return (struct sti_vtg *)platform_get_drvdata(pdev);
> > + vtg = platform_get_drvdata(pdev);
> > +
> > + put_device(&pdev->dev);
>
> I would prefer of_node_put() instead, which does the same basically, but
> at least it is more obviously linked to of_find_device_by_node().

of_node_put() operates on OF nodes, but here it is the platform device
that is leaking.

> > +
> > + return vtg;
> > }

Johan