On Thu, 21 May 2020 15:05:37 -0400
"Andrew F. Davis" <afd@xxxxxx> wrote:
> 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.
Applied to the fixes-togreg branch of iio.git and marked for stable.
These won't go anywhere now until after the merge window.
Thanks,
Jonathan
>
> > 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);
> >>>>>>
> >>>>>>
> >>>>
> >>
> >
