On 5/21/20 2:45 PM, Jonathan Cameron wrote:
> On Thu, 21 May 2020 15:44:43 +0100
> Jonathan Cameron <jic23@xxxxxxxxxxxxxxxxxxxxx> wrote:
>
>> On 21 May 2020 14:11:10 BST, "Andrew F. Davis" <afd@xxxxxx> wrote:
>>>
>>>
>>> On 5/18/20 12:06 PM, Jonathan Cameron wrote:
>>>>
>>>>
>>>> On 18 May 2020 01:09:47 BST, "Andrew F. Davis" <afd@xxxxxx> wrote:
>>>>> On 5/17/20 1:29 PM, jic23@xxxxxxxxxx wrote:
>>>>>> From: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
>>>>>>
>>>>>> One of a class of bugs pointed out by Lars in a recent review.
>>>>>> iio_push_to_buffers_with_timestamp assumes the buffer used is
>>> aligned
>>>>>> to the size of the timestamp (8 bytes). This is not guaranteed in
>>>>>> this driver which uses a 32 byte array of smaller elements on the
>>>>> stack.
>>>>>> As Lars also noted this anti pattern can involve a leak of data to
>>>>>> userspace and that indeed can happen here. We close both issues by
>>>>>> moving to a suitable structure in the iio_priv() data with
>>> alignment
>>>>>> explicitly requested. This data is allocated with kzalloc so no
>>>>>> data can leak appart from previous readings.
>>>>>>
>>>>>> Fixes: eec96d1e2d31 ("iio: health: Add driver for the TI AFE4403
>>>>> heart monitor")
>>>>>> Reported-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
>>>>>> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
>>>>>> Cc: Andrew F. Davis <afd@xxxxxx>
>>>>>> ---
>>>>>> drivers/iio/health/afe4403.c | 9 ++++++---
>>>>>> 1 file changed, 6 insertions(+), 3 deletions(-)
>>>>>>
>>>>>> diff --git a/drivers/iio/health/afe4403.c
>>>>> b/drivers/iio/health/afe4403.c
>>>>>> index e9f87e42ff4f..a3507624b30f 100644
>>>>>> --- a/drivers/iio/health/afe4403.c
>>>>>> +++ b/drivers/iio/health/afe4403.c
>>>>>> @@ -65,6 +65,7 @@ static const struct reg_field
>>> afe4403_reg_fields[]
>>>>> = {
>>>>>> * @regulator: Pointer to the regulator for the IC
>>>>>> * @trig: IIO trigger for this device
>>>>>> * @irq: ADC_RDY line interrupt number
>>>>>> + * @buffer: Used to construct data layout to push into IIO buffer.
>>>>>> */
>>>>>> struct afe4403_data {
>>>>>> struct device *dev;
>>>>>> @@ -74,6 +75,8 @@ struct afe4403_data {
>>>>>> struct regulator *regulator;
>>>>>> struct iio_trigger *trig;
>>>>>> int irq;
>>>>>> + /* Ensure suitable alignment for timestamp */
>>>>>> + s32 buffer[8] __aligned(8);
>>>>>
>>>>>
>>>>> One of those fancy structs with the timestamp specified would be
>>> nice
>>>>> here like the other patches. IIRC we have 6 s32 channels, plus a s64
>>>>> ts.
>>>>
>>>> I think we may only have some of those channels enabled. So ts may
>>> be it several
>>>> locations in the buffer.
>>>>
>>>
>>> Might have been better to have the ts at the beginning, could have also
>>> helped with alignment for when an odd number of channels are enabled.
>>
>> Perhaps but for many use cases we don't turn timestamps on and we would need to pad
>> anyway for alignment of the fifo.
>>
>>>
>>>> Hence we could use the structure approach but it might give a false
>>> sense
>>>> of what is going on.
>>>>
>>>
>>> That's true, it can always be cleaned later then.
>>
>> Agreed. This is definitely something we can revisit sometime in the future.
>
> Formal Ack on applying the two afe patches?
>
Acked-by: Andrew F. Davis <afd@xxxxxx>
> Thanks,
>
> Jonathan
>>
>> J
>>>
>>> Andrew
>>>
>>>> J
>>>>>
>>>>> Other than that everything looks good.
>>>>>
>>>>> Andrew
>>>>>
>>>>>
>>>>>> };
>>>>>>
>>>>>> enum afe4403_chan_id {
>>>>>> @@ -309,7 +312,6 @@ static irqreturn_t afe4403_trigger_handler(int
>>>>> irq, void *private)
>>>>>> struct iio_dev *indio_dev = pf->indio_dev;
>>>>>> struct afe4403_data *afe = iio_priv(indio_dev);
>>>>>> int ret, bit, i = 0;
>>>>>> - s32 buffer[8];
>>>>>> u8 tx[4] = {AFE440X_CONTROL0, 0x0, 0x0, AFE440X_CONTROL0_READ};
>>>>>> u8 rx[3];
>>>>>>
>>>>>> @@ -326,7 +328,7 @@ static irqreturn_t afe4403_trigger_handler(int
>>>>> irq, void *private)
>>>>>> if (ret)
>>>>>> goto err;
>>>>>>
>>>>>> - buffer[i++] = get_unaligned_be24(&rx[0]);
>>>>>> + afe->buffer[i++] = get_unaligned_be24(&rx[0]);
>>>>>> }
>>>>>>
>>>>>> /* Disable reading from the device */
>>>>>> @@ -335,7 +337,8 @@ static irqreturn_t afe4403_trigger_handler(int
>>>>> irq, void *private)
>>>>>> if (ret)
>>>>>> goto err;
>>>>>>
>>>>>> - iio_push_to_buffers_with_timestamp(indio_dev, buffer,
>>>>> pf->timestamp);
>>>>>> + iio_push_to_buffers_with_timestamp(indio_dev, afe->buffer,
>>>>>> + pf->timestamp);
>>>>>> err:
>>>>>> iio_trigger_notify_done(indio_dev->trig);
>>>>>>
>>>>>>
>>>>
>>
>
