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

[Jonathan Cameron]

On Sat, 24 Jul 2021 16:48:40 +0100
Jonathan Cameron <jic23 at kernel.org> wrote:

> On Mon, 19 Jul 2021 19:53:11 +0000
> Yizhuo <yzhai003 at 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 at 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?

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),  
>