linux-kernel - Re: [PATCH] iio: adc: palmas: fix off by one bugs

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Date:   Sat, 29 Apr 2023 22:25:38 +0200
From:   Patrik Dahlström <risca@...akolonin.se>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Dan Carpenter <dan.carpenter@...aro.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-janitors@...r.kernel.org
Subject: Re: [PATCH] iio: adc: palmas: fix off by one bugs

On Sun, Apr 23, 2023 at 02:11:24PM +0100, Jonathan Cameron wrote:
> On Fri, 21 Apr 2023 13:41:56 +0300
> Dan Carpenter <dan.carpenter@...aro.org> wrote:
> 
> > Valid values for "adc_chan" are zero to (PALMAS_ADC_CH_MAX - 1).
> > Smatch detects some buffer overflows caused by this:
> > drivers/iio/adc/palmas_gpadc.c:721 palmas_gpadc_read_event_value() error: buffer overflow 'adc->thresholds' 16 <= 16
> > drivers/iio/adc/palmas_gpadc.c:758 palmas_gpadc_write_event_value() error: buffer overflow 'adc->thresholds' 16 <= 16
> > 
> > The effect of this bug in other functions is more complicated but
> > obviously we should fix all of them.
> > 
> > Fixes: a99544c6c883 ("iio: adc: palmas: add support for iio threshold events")
> > Signed-off-by: Dan Carpenter <dan.carpenter@...aro.org>
> 
> Looks good to me.  Slight shuffle at the moment will delay me applying this.
> 
> I'll wait for Linus to pick up Greg's pull request then rebase my fixes branch
> on top of that.  Otherwise I make a mess of linux-next ordering and things might
> blow up.
> 
> In meantime, Patrik, please take a look.

Sorry for the long delay.

The changes look good to me. I've checked all other uses of adc_chan in the
code and they all seem to be guarded by the checks below.

Best regards
Patrik

> 
> Jonathan
> 
> > ---
> > ---
> >  drivers/iio/adc/palmas_gpadc.c | 10 +++++-----
> >  1 file changed, 5 insertions(+), 5 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/palmas_gpadc.c b/drivers/iio/adc/palmas_gpadc.c
> > index c1c439215aeb..7dfc9c927a23 100644
> > --- a/drivers/iio/adc/palmas_gpadc.c
> > +++ b/drivers/iio/adc/palmas_gpadc.c
> > @@ -547,7 +547,7 @@ static int palmas_gpadc_read_raw(struct iio_dev *indio_dev,
> >  	int adc_chan = chan->channel;
> >  	int ret = 0;
> >  
> > -	if (adc_chan > PALMAS_ADC_CH_MAX)
> > +	if (adc_chan >= PALMAS_ADC_CH_MAX)
> >  		return -EINVAL;
> >  
> >  	mutex_lock(&adc->lock);
> > @@ -595,7 +595,7 @@ static int palmas_gpadc_read_event_config(struct iio_dev *indio_dev,
> >  	int adc_chan = chan->channel;
> >  	int ret = 0;
> >  
> > -	if (adc_chan > PALMAS_ADC_CH_MAX || type != IIO_EV_TYPE_THRESH)
> > +	if (adc_chan >= PALMAS_ADC_CH_MAX || type != IIO_EV_TYPE_THRESH)
> >  		return -EINVAL;
> >  
> >  	mutex_lock(&adc->lock);
> > @@ -684,7 +684,7 @@ static int palmas_gpadc_write_event_config(struct iio_dev *indio_dev,
> >  	int adc_chan = chan->channel;
> >  	int ret;
> >  
> > -	if (adc_chan > PALMAS_ADC_CH_MAX || type != IIO_EV_TYPE_THRESH)
> > +	if (adc_chan >= PALMAS_ADC_CH_MAX || type != IIO_EV_TYPE_THRESH)
> >  		return -EINVAL;
> >  
> >  	mutex_lock(&adc->lock);
> > @@ -710,7 +710,7 @@ static int palmas_gpadc_read_event_value(struct iio_dev *indio_dev,
> >  	int adc_chan = chan->channel;
> >  	int ret;
> >  
> > -	if (adc_chan > PALMAS_ADC_CH_MAX || type != IIO_EV_TYPE_THRESH)
> > +	if (adc_chan >= PALMAS_ADC_CH_MAX || type != IIO_EV_TYPE_THRESH)
> >  		return -EINVAL;
> >  
> >  	mutex_lock(&adc->lock);
> > @@ -744,7 +744,7 @@ static int palmas_gpadc_write_event_value(struct iio_dev *indio_dev,
> >  	int old;
> >  	int ret;
> >  
> > -	if (adc_chan > PALMAS_ADC_CH_MAX || type != IIO_EV_TYPE_THRESH)
> > +	if (adc_chan >= PALMAS_ADC_CH_MAX || type != IIO_EV_TYPE_THRESH)
> >  		return -EINVAL;
> >  
> >  	mutex_lock(&adc->lock);
>