linux-kernel - Re: [PATCH] i2c: rcar: fix a possible NULL dereference

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Date:	Thu, 12 Nov 2015 08:52:38 +0100
From:	Wolfram Sang <wsa@...-dreams.de>
To:	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:	LABBE Corentin <clabbe.montjoie@...il.com>,
	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] i2c: rcar: fix a possible NULL dereference

On Thu, Nov 12, 2015 at 08:44:47AM +0100, Uwe Kleine-König wrote:
> Hello,
> 
> On Thu, Nov 12, 2015 at 08:25:09AM +0100, LABBE Corentin wrote:
> > of_match_device could return NULL, and so cause a NULL pointer
> > dereference later.
> > 
> > Reported-by: coverity (CID 1130036)
> > Signed-off-by: LABBE Corentin <clabbe.montjoie@...il.com>
> > ---
> >  drivers/i2c/busses/i2c-rcar.c | 6 +++++-
> >  1 file changed, 5 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/i2c/busses/i2c-rcar.c b/drivers/i2c/busses/i2c-rcar.c
> > index b0ae560..d2bdbda 100644
> > --- a/drivers/i2c/busses/i2c-rcar.c
> > +++ b/drivers/i2c/busses/i2c-rcar.c
> > @@ -639,6 +639,7 @@ static int rcar_i2c_probe(struct platform_device *pdev)
> >  	struct device *dev = &pdev->dev;
> >  	u32 bus_speed;
> >  	int irq, ret;
> > +	const struct of_device_id *of_id;
> >  
> >  	priv = devm_kzalloc(dev, sizeof(struct rcar_i2c_priv), GFP_KERNEL);
> >  	if (!priv)
> > @@ -653,7 +654,10 @@ static int rcar_i2c_probe(struct platform_device *pdev)
> >  	bus_speed = 100000; /* default 100 kHz */
> >  	of_property_read_u32(dev->of_node, "clock-frequency", &bus_speed);
> >  
> > -	priv->devtype = (enum rcar_i2c_type)of_match_device(rcar_i2c_dt_ids, dev)->data;
> > +	of_id = of_match_device(rcar_i2c_dt_ids, dev);
> > +	if (!of_id)
> > +		return -ENODEV;
> > +	priv->devtype = (enum rcar_i2c_type)of_id->data;
> 
> This is nearly an open coding of of_device_get_match_data. Maybe using
> 
> 	priv->devtype = (enum rcar_i2c_type)of_device_get_match_data(dev)
> 
> if good enough? 
> 
> Other than that, the NULL pointer dereference should only happen if the
> device was bound using the driver name. That might be worth to point out
> in the commit log. So maybe make (in a separate patch) the probe
> function fail when probed by name?

RCar is a DT only platform.


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