Re: [PATCH] iio: adc: imx93: fix a signedness bug in imx93_adc_read_raw()

[Jonathan Cameron <jic23@kernel.org>]

On Wed, 15 Feb 2023 02:16:40 +0000
Bough Chen <haibo.chen@nxp.com> wrote:

> > -----Original Message-----
> > From: Dan Carpenter <error27@gmail.com>
> > Sent: 2023年2月14日 23:48
> > To: Bough Chen <haibo.chen@nxp.com>
> > Cc: Jonathan Cameron <jic23@kernel.org>; Lars-Peter Clausen
> > <lars@metafoo.de>; Shawn Guo <shawnguo@kernel.org>; Sascha Hauer
> > <s.hauer@pengutronix.de>; Pengutronix Kernel Team
> > <kernel@pengutronix.de>; Fabio Estevam <festevam@gmail.com>; dl-linux-imx
> > <linux-imx@nxp.com>; linux-iio@vger.kernel.org;
> > kernel-janitors@vger.kernel.org
> > Subject: [PATCH] iio: adc: imx93: fix a signedness bug in imx93_adc_read_raw()
> > 
> > The problem is these lines:
> > 
> > 	ret = vref_uv = regulator_get_voltage(adc->vref);
> > 	if (ret < 0)
> > 
> > The "ret" variable is type long and "vref_uv" is u32 so that means the condition
> > can never be true on a 64bit system.  A negative error code from
> > regulator_get_voltage() would be cast to a high positive
> > u32 value and then remain a high positive value when cast to a long.
> > 
> > The "ret" variable only ever stores ints so it should be declared as an int.  We
> > can delete the "vref_uv" variable and use "ret" directly.  
> 
> Thanks for the catching!
> 
> Reviewed-by: Haibo Chen <haibo.chen@nxp.com>

Applied to the fixes-togreg branch of iio.git.

Thanks

Jonathan

> 
> Best Regards
> Haibo Chen
> > 
> > Fixes: 7d02296ac8b8 ("iio: adc: add imx93 adc support")
> > Signed-off-by: Dan Carpenter <error27@gmail.com>
> > ---
> >  drivers/iio/adc/imx93_adc.c | 7 +++----
> >  1 file changed, 3 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/imx93_adc.c b/drivers/iio/adc/imx93_adc.c index
> > d8de8284e13d..8c68f0cd48f2 100644
> > --- a/drivers/iio/adc/imx93_adc.c
> > +++ b/drivers/iio/adc/imx93_adc.c
> > @@ -236,8 +236,7 @@ static int imx93_adc_read_raw(struct iio_dev
> > *indio_dev,  {
> >  	struct imx93_adc *adc = iio_priv(indio_dev);
> >  	struct device *dev = adc->dev;
> > -	long ret;
> > -	u32 vref_uv;
> > +	int ret;
> > 
> >  	switch (mask) {
> >  	case IIO_CHAN_INFO_RAW:
> > @@ -253,10 +252,10 @@ static int imx93_adc_read_raw(struct iio_dev
> > *indio_dev,
> >  		return IIO_VAL_INT;
> > 
> >  	case IIO_CHAN_INFO_SCALE:
> > -		ret = vref_uv = regulator_get_voltage(adc->vref);
> > +		ret = regulator_get_voltage(adc->vref);
> >  		if (ret < 0)
> >  			return ret;
> > -		*val = vref_uv / 1000;
> > +		*val = ret / 1000;
> >  		*val2 = 12;
> >  		return IIO_VAL_FRACTIONAL_LOG2;
> > 
> > --
> > 2.35.1  
>