linux-kernel - Re: [PATCH] iio: adc: imx25-gcq: Variable could be uninitialized if regmap

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Date:   Tue, 1 Oct 2019 09:54:46 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Marco Felsch <m.felsch@...gutronix.de>
Cc:     Yizhuo <yzhai003@....edu>, csong@...ucr.edu,
        Kate Stewart <kstewart@...uxfoundation.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Allison Randal <allison@...utok.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Enrico Weigelt <info@...ux.net>,
        Fabio Estevam <festevam@...il.com>,
        Sascha Hauer <s.hauer@...gutronix.de>, zhiyunq@...ucr.edu,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        NXP Linux Team <linux-imx@....com>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Hartmut Knaack <knaack.h@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        Shawn Guo <shawnguo@...nel.org>,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] iio: adc: imx25-gcq: Variable could be uninitialized if
 regmap_read() fails

On Mon, 30 Sep 2019 09:44:12 +0200
Marco Felsch <m.felsch@...gutronix.de> wrote:

> Hi Yizhuo,
> 
> thanks for your patch.
> 
> On 19-09-27 17:28, Yizhuo wrote:
> > In function mx25_gcq_irq(), local variable "stats" could
> > be uninitialized if function regmap_read() returns -EINVAL.
> > However, this value is used in if statement, which is
> > potentially unsafe. The same case applied to the variable
> > "data" in function mx25_gcq_get_raw_value() in the same file.  
> 
> IMHO the commit header should be something like: "iio: adc: imx25-gcq:
> fix uninitialized variable usage"...
> 
> and please add a fixes tag.
As with the others, before adding a fixes tag, please verify there
is an actual path to trigger this.

In this case it's an mmio regmap with no clock. For those, I'm not sure
if there is a failure path.

Still a worthwhile hardening / cleanup patch, but shouldn't be called
a fix or marked with a fixes tag because we don't want people to think
it is necessary to backport it.

Thanks,

Jonathan


> 
> > 
> > Signed-off-by: Yizhuo <yzhai003@....edu>
> > ---
> >  drivers/iio/adc/fsl-imx25-gcq.c | 10 ++++++++--
> >  1 file changed, 8 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/fsl-imx25-gcq.c b/drivers/iio/adc/fsl-imx25-gcq.c
> > index df19ecae52f7..dbf3e8e85aba 100644
> > --- a/drivers/iio/adc/fsl-imx25-gcq.c
> > +++ b/drivers/iio/adc/fsl-imx25-gcq.c
> > @@ -74,7 +74,10 @@ static irqreturn_t mx25_gcq_irq(int irq, void *data)
> >  	struct mx25_gcq_priv *priv = data;
> >  	u32 stats;
> >  
> > -	regmap_read(priv->regs, MX25_ADCQ_SR, &stats);
> > +	int ret = regmap_read(priv->regs, MX25_ADCQ_SR, &stats);  
> 
> Please don't do this. First declare the variable and then use it.
> 
> Regards,
>   Marco
> 
> > +
> > +	if (ret)
> > +		return ret;
> >  
> >  	if (stats & MX25_ADCQ_SR_EOQ) {
> >  		regmap_update_bits(priv->regs, MX25_ADCQ_MR,
> > @@ -121,7 +124,10 @@ static int mx25_gcq_get_raw_value(struct device *dev,
> >  		return -ETIMEDOUT;
> >  	}
> >  
> > -	regmap_read(priv->regs, MX25_ADCQ_FIFO, &data);
> > +	int ret = regmap_read(priv->regs, MX25_ADCQ_FIFO, &data);
> > +
> > +	if (ret)
> > +		return ret;
> >  
> >  	*val = MX25_ADCQ_FIFO_DATA(data);
> >  
> > -- 
> > 2.17.1
> > 
> > 
> >   
>