linux-kernel - Re: [PATCH] drm/bridge: it6505: Fix potential NULL dereference

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Date: Sun, 9 Jun 2024 23:59:00 +0300
From: Dan Carpenter <dan.carpenter@...aro.org>
To: Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc: Allen Chen <allen.chen@....com.tw>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>,
	Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
	Jonas Karlman <jonas@...boo.se>,
	Jernej Skrabec <jernej.skrabec@...il.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>,
	Hermes Wu <hermes.wu@....com.tw>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] drm/bridge: it6505: Fix potential NULL dereference

On Sun, Jun 09, 2024 at 10:38:39PM +0300, Dmitry Baryshkov wrote:
> On Sat, Jun 08, 2024 at 05:21:08PM +0300, Dan Carpenter wrote:
> > Smatch complains correctly that the NULL checking isn't consistent:
> > 
> >     drivers/gpu/drm/bridge/ite-it6505.c:2583 it6505_poweron()
> >     error: we previously assumed 'pdata->pwr18' could be null
> >     (see line 2569)
> > 
> > Add a NULL check to prevent a NULL dereference on the error path.
> > 
> > Fixes: b5c84a9edcd4 ("drm/bridge: add it6505 driver")
> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> > ---
> >  drivers/gpu/drm/bridge/ite-it6505.c | 3 ++-
> >  1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/gpu/drm/bridge/ite-it6505.c b/drivers/gpu/drm/bridge/ite-it6505.c
> > index 3f68c82888c2..4f01fadaec0f 100644
> > --- a/drivers/gpu/drm/bridge/ite-it6505.c
> > +++ b/drivers/gpu/drm/bridge/ite-it6505.c
> > @@ -2580,7 +2580,8 @@ static int it6505_poweron(struct it6505 *it6505)
> >  		usleep_range(1000, 2000);
> >  		err = regulator_enable(pdata->ovdd);
> >  		if (err) {
> > -			regulator_disable(pdata->pwr18);
> > +			if (pdata->pwr18)
> > +				regulator_disable(pdata->pwr18);
> 
> Wait... I wat too quick to R-B it. The driver uses devm_regulator_get(),
> which always returns non-NULL result. So all `if (pdata->pwr18)` and
> `if (pdata->ovdd)` checks in the driver are useless. Could you please
> send a patch, removing them?
> 

Sure.  Will do.

regards,
dan carpenter