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

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

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

>>
>> 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),
>>>
>>
>

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