linux-kernel - Re: [PATCH] drm/logicvc: Fix device node reference leak in logicvc_drm_config

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Message-ID: <20260203143531.1ab9a19c@kmaincent-XPS-13-7390>
Date: Tue, 3 Feb 2026 14:35:31 +0100
From: Kory Maincent <kory.maincent@...tlin.com>
To: Felix Gu <ustc.gu@...il.com>
Cc: Paul Kocialkowski <paulk@...-base.io>, Maarten Lankhorst
 <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>,
 Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>,
 Simona Vetter <simona@...ll.ch>, Paul Kocialkowski
 <paul.kocialkowski@...tlin.com>, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH] drm/logicvc: Fix device node reference leak in
 logicvc_drm_config_parse()

On Tue, 3 Feb 2026 10:57:47 +0100
Kory Maincent <kory.maincent@...tlin.com> wrote:

> On Fri, 30 Jan 2026 00:21:19 +0800
> Felix Gu <ustc.gu@...il.com> wrote:
> 
> > The logicvc_drm_config_parse() function calls of_get_child_by_name() to
> > find the "layers" node but fails to release the reference, leading to a
> > device node reference leak.
> > 
> > Fix this by using the __free(device_node) cleanup attribute to automatic
> > release the reference when the variable goes out of scope.
> > 
> > Fixes: efeeaefe9be5 ("drm: Add support for the LogiCVC display controller")
> > Signed-off-by: Felix Gu <ustc.gu@...il.com>
> > ---
> >  drivers/gpu/drm/logicvc/logicvc_drm.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/gpu/drm/logicvc/logicvc_drm.c
> > b/drivers/gpu/drm/logicvc/logicvc_drm.c index 204b0fee55d0..bbebf4fc7f51
> > 100644 --- a/drivers/gpu/drm/logicvc/logicvc_drm.c
> > +++ b/drivers/gpu/drm/logicvc/logicvc_drm.c
> > @@ -92,7 +92,6 @@ static int logicvc_drm_config_parse(struct logicvc_drm
> > *logicvc) struct device *dev = drm_dev->dev;
> >  	struct device_node *of_node = dev->of_node;
> >  	struct logicvc_drm_config *config = &logicvc->config;
> > -	struct device_node *layers_node;
> >  	int ret;
> >  
> >  	logicvc_of_property_parse_bool(of_node,
> > LOGICVC_OF_PROPERTY_DITHERING, @@ -128,7 +127,8 @@ static int
> > logicvc_drm_config_parse(struct logicvc_drm *logicvc) if (ret)
> >  		return ret;
> >  
> > -	layers_node = of_get_child_by_name(of_node, "layers");
> > +	struct device_node *layers_node __free(device_node) =
> > +		of_get_child_by_name(of_node, "layers");  
> 
> We usualy don't declare variable in the middle of a function.
> You should rather simply change the declaration line at the top like this:
> struct device_node *layers_node __free(device_node) = NULL;

It seems Linus disagree on this topic and I understand his arguments:
https://lore.kernel.org/all/CAHk-=whPZoi03ZwphxiW6cuWPtC3nyKYS8_BThgztCdgPWP1WA@mail.gmail.com/
https://lore.kernel.org/all/CAHk-=wiCOTW5UftUrAnvJkr6769D29tF7Of79gUjdQHS_TkF5A@mail.gmail.com/

Then, ok to me:
Reviewed-by: Kory Maincent <kory.maincent@...tlin.com>

Thank you!
-- 
Köry Maincent, Bootlin
Embedded Linux and kernel engineering
https://bootlin.com