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?
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);
> >>>>
> >>>>
> >>
>
