linux-kernel - Re: [PATCH 1/6] drm/bridge: aux-hpd: fix OF node leaks

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Date: Tue, 20 Feb 2024 15:35:35 +0200
From: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
To: Julia Lawall <julia.lawall@...ia.fr>
Cc: Johan Hovold <johan@...nel.org>, Markus Elfring <Markus.Elfring@....de>, 
	Johan Hovold <johan+linaro@...nel.org>, freedreno@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, linux-phy@...ts.infradead.org, 
	linux-arm-msm@...r.kernel.org, kernel-janitors@...r.kernel.org, 
	Andrzej Hajda <andrzej.hajda@...el.com>, Bjorn Andersson <andersson@...nel.org>, 
	Daniel Vetter <daniel@...ll.ch>, David Airlie <airlied@...il.com>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, 
	Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>, 
	Thomas Zimmermann <tzimmermann@...e.de>, Vinod Koul <vkoul@...nel.org>, 
	LKML <linux-kernel@...r.kernel.org>, Abhinav Kumar <quic_abhinavk@...cinc.com>, 
	Jernej Skrabec <jernej.skrabec@...il.com>, Jonas Karlman <jonas@...boo.se>, 
	Kishon Vijay Abraham I <kishon@...nel.org>, Konrad Dybcio <konrad.dybcio@...aro.org>, 
	Kuogee Hsieh <quic_khsieh@...cinc.com>, 
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>, Rob Clark <robdclark@...il.com>
Subject: Re: [PATCH 1/6] drm/bridge: aux-hpd: fix OF node leaks

On Tue, 20 Feb 2024 at 14:56, Julia Lawall <julia.lawall@...ia.fr> wrote:
>
>
>
> On Tue, 20 Feb 2024, Dmitry Baryshkov wrote:
>
> > On Tue, 20 Feb 2024 at 13:52, Julia Lawall <julia.lawall@...ia.fr> wrote:
> > >
> > >
> > >
> > > On Tue, 20 Feb 2024, Johan Hovold wrote:
> > >
> > > > On Mon, Feb 19, 2024 at 06:48:30PM +0100, Markus Elfring wrote:
> > > > > > The two device node references taken during allocation need to be
> > > > > > dropped when the auxiliary device is freed.
> > > > > …
> > > > > > +++ b/drivers/gpu/drm/bridge/aux-hpd-bridge.c
> > > > > …
> > > > > > @@ -74,6 +75,8 @@ struct device *drm_dp_hpd_bridge_register(struct device *parent,
> > > > > >
> > > > > >   ret = auxiliary_device_init(adev);
> > > > > >   if (ret) {
> > > > > > +         of_node_put(adev->dev.platform_data);
> > > > > > +         of_node_put(adev->dev.of_node);
> > > > > >           ida_free(&drm_aux_hpd_bridge_ida, adev->id);
> > > > > >           kfree(adev);
> > > > > >           return ERR_PTR(ret);
> > > > >
> > > > > The last two statements are also used in a previous if branch.
> > > > > https://elixir.bootlin.com/linux/v6.8-rc5/source/drivers/gpu/drm/bridge/aux-hpd-bridge.c#L63
> > > > >
> > > > > How do you think about to avoid such a bit of duplicate source code
> > > > > by adding a label here?
> > > >
> > > > No, the current code is fine and what you are suggesting is in any case
> > > > unrelated to this fix.
> > > >
> > > > If this function ever grows a third error path like that, I too would
> > > > consider it however.
> > >
> > > I guess these of_node_puts can all go away shortly with cleanup anyway?
> >
> > I'm not sure about it. Those are long-living variables, so they are
> > not a subject of cleanup.h, are they?
>
> OK, I didn't look at this code in detail, but cleanup would just call
> of_node_put, not actually free the data.

Yes. The nodes should be put either in case of the failure or (if
everything goes fine) at the device unregistration.

-- 
With best wishes
Dmitry