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

Hi,

On 10/3/21 5:47 PM, Jonathan Cameron wrote:

On Sun, 8 Aug 2021 18:32:43 +0100
Jonathan Cameron [off-list ref] wrote:

quoted

On Sat, 24 Jul 2021 16:48:40 +0100
Jonathan Cameron [off-list ref] wrote:

quoted

On Mon, 19 Jul 2021 19:53:11 +0000
Yizhuo [off-list ref] wrote:
   

quoted

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 <redacted>

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

I cannot see side effects with reordering itself.
However, if we get an error with the read access, just leaving with
irq_handled status is probably not enough.
In such case we are facing a serious issue and it would make sense to 
return irq_none instead, as the interrupt will probably never be 
acknowledged.

BRs

quoted

Thanks,

Jonathan

quoted

quoted

---
  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
   

quoted

+	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),

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