Re: [PATCH] iio: adc: stm32-dfsdm: Fix the uninitialized use if regmap_read() fails

From: Jonathan Cameron <jic23@kernel.org>
To: Yizhuo <yzhai003@ucr.edu>,
	Mugilraj Dhavachelvan <dmugil2000@gmail.com>,
	Olivier Moysan <olivier.moysan@st.com>,
	Krzysztof Kozlowski <krzk@kernel.org>,
	Arnaud Pouliquen <arnaud.pouliquen@st.com>,
	linux-stm32@st-md-mailman.stormreply.com
Cc: Lars-Peter Clausen <lars@metafoo.de>,
	Maxime Coquelin <mcoquelin.stm32@gmail.com>,
	Alexandre Torgue <alexandre.torgue@foss.st.com>,
	Andy Shevchenko <andy.shevchenko@gmail.com>,
	Mark Brown <broonie@kernel.org>,
	linux-iio@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] iio: adc: stm32-dfsdm: Fix the uninitialized use if regmap_read() fails
Date: Sun, 3 Oct 2021 16:47:26 +0100	[thread overview]
Message-ID: <20211003164726.42e20526@jic23-huawei> (raw)
In-Reply-To: <20210808183243.70619aa8@jic23-huawei>

On Sun, 8 Aug 2021 18:32:43 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> On Sat, 24 Jul 2021 16:48:40 +0100
> Jonathan Cameron <jic23@kernel.org> wrote:
> 
> > On Mon, 19 Jul 2021 19:53:11 +0000
> > Yizhuo <yzhai003@ucr.edu> wrote:
> >   
> > > Inside function stm32_dfsdm_irq(), the variable "status", "int_en"
> > > could be uninitialized if the regmap_read() fails and returns an error
> > > code.  However, they are directly used in the later context to decide
> > > the control flow, which is potentially unsafe.
> > > 
> > > Fixes: e2e6771c64625 ("IIO: ADC: add STM32 DFSDM sigma delta ADC support")
> > > 
> > > Signed-off-by: Yizhuo <yzhai003@ucr.edu>    
> > 
> > Hi Yizhou
> > 
> > I want to get some review of this from people familiar with the
> > hardware as there is a small possibility your reordering might have
> > introduced a problem.  
> 
> To stm32 people, can someone take a look at this?

This one is still outstanding.  If anyone from stm32 side of things could take a look
that would be great,

Jonathan

> 
> Thanks,
> 
> Jonathan
> 
> >   
> > > ---
> > >  drivers/iio/adc/stm32-dfsdm-adc.c | 9 +++++++--
> > >  1 file changed, 7 insertions(+), 2 deletions(-)
> > > 
> > > diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
> > > index 1cfefb3b5e56..d8b78aead942 100644
> > > --- a/drivers/iio/adc/stm32-dfsdm-adc.c
> > > +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
> > > @@ -1292,9 +1292,11 @@ static irqreturn_t stm32_dfsdm_irq(int irq, void *arg)
> > >  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
> > >  	struct regmap *regmap = adc->dfsdm->regmap;
> > >  	unsigned int status, int_en;
> > > +	int ret;
> > >  
> > > -	regmap_read(regmap, DFSDM_ISR(adc->fl_id), &status);
> > > -	regmap_read(regmap, DFSDM_CR2(adc->fl_id), &int_en);    
> > 
> > Moving this later is only valid if there aren't any side effects.
> > The current ordering is strange enough it makes me wonder if there might be!
> > 
> > Jonathan
> >   
> > > +	ret = regmap_read(regmap, DFSDM_ISR(adc->fl_id), &status);
> > > +	if (ret)
> > > +		return IRQ_HANDLED;
> > >  
> > >  	if (status & DFSDM_ISR_REOCF_MASK) {
> > >  		/* Read the data register clean the IRQ status */
> > > @@ -1303,6 +1305,9 @@ static irqreturn_t stm32_dfsdm_irq(int irq, void *arg)
> > >  	}
> > >  
> > >  	if (status & DFSDM_ISR_ROVRF_MASK) {
> > > +		ret = regmap_read(regmap, DFSDM_CR2(adc->fl_id), &int_en);
> > > +		if (ret)
> > > +			return IRQ_HANDLED;
> > >  		if (int_en & DFSDM_CR2_ROVRIE_MASK)
> > >  			dev_warn(&indio_dev->dev, "Overrun detected\n");
> > >  		regmap_update_bits(regmap, DFSDM_ICR(adc->fl_id),    
> >   
> 