linux-kernel - Re: [PATCH] iio: max9611: fix a NULL pointer dereference

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Message-ID: <20190309183437.479f90a1@archlinux>
Date:   Sat, 9 Mar 2019 18:34:37 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Tomasz Duszynski <tduszyns@...il.com>
Cc:     Kangjie Lu <kjlu@....edu>, pakki001@....edu,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Stefan Agner <stefan@...er.ch>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] iio: max9611: fix a NULL pointer dereference

On Sat, 9 Mar 2019 16:19:17 +0100
Tomasz Duszynski <tduszyns@...il.com> wrote:

> On Fri, Mar 08, 2019 at 10:51:40PM -0600, Kangjie Lu wrote:
> > of_match_device may return NULL when it fails, and in this case,
> > there will be a NULL pointer dereference. The fix returns
> > EINVAL when of_match_device returns NULL.
> >
> > Signed-off-by: Kangjie Lu <kjlu@....edu>
> > ---
> >  drivers/iio/adc/max9611.c | 7 +++++--
> >  1 file changed, 5 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/iio/adc/max9611.c b/drivers/iio/adc/max9611.c
> > index 917223d5ff5b..531b6614ea29 100644
> > --- a/drivers/iio/adc/max9611.c
> > +++ b/drivers/iio/adc/max9611.c
> > @@ -524,13 +524,16 @@ static int max9611_probe(struct i2c_client *client,
> >  {
> >  	const char * const shunt_res_prop = "shunt-resistor-micro-ohms";
> >  	const struct device_node *of_node = client->dev.of_node;
> > -	const struct of_device_id *of_id =
> > -		of_match_device(max9611_of_table, &client->dev);  
> 
> Given we got to this point how this can go wrong?

If this is to squash a warning then there may be some argument
even though it can't actually fail.  If there is such a warning
please put it in the patch description.

Thanks,

Jonathan

> 
> > +	const struct of_device_id *of_id;
> >  	struct max9611_dev *max9611;
> >  	struct iio_dev *indio_dev;
> >  	unsigned int of_shunt;
> >  	int ret;
> >
> > +	of_id = of_match_device(max9611_of_table, &client->dev);
> > +	if (!of_id)
> > +		return -EINVAL;
> > +
> >  	indio_dev = devm_iio_device_alloc(&client->dev, sizeof(*max9611));
> >  	if (!indio_dev)
> >  		return -ENOMEM;
> > --
> > 2.17.1
> >