On Wed, 22 Jul 2020 16:51:03 +0100
Jonathan Cameron <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 an 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.
>
> This data is allocated with kzalloc so no data can leak apart
> from previous readings.
>
> The explicit alignment of ts is necessary to ensure correct padding
> on architectures where s64 is only 4 bytes aligned such as x86_32.
>
> Fixes: a9e9c7153e96 ("iio: adc: add max1117/max1118/max1119 ADC driver")
> Reported-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> Cc: Akinobu Mita <akinobu.mita@xxxxxxxxx>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Applied and marked for stable.
Thanks,
Jonathan
> ---
> drivers/iio/adc/max1118.c | 10 +++++++---
> 1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/adc/max1118.c b/drivers/iio/adc/max1118.c
> index 01b20e420ac4..6efb0b43d938 100644
> --- a/drivers/iio/adc/max1118.c
> +++ b/drivers/iio/adc/max1118.c
> @@ -36,6 +36,11 @@ struct max1118 {
> struct spi_device *spi;
> struct mutex lock;
> struct regulator *reg;
> + /* Ensure natural alignment of buffer elements */
> + struct {
> + u8 channels[2];
> + s64 ts __aligned(8);
> + } scan;
>
> u8 data ____cacheline_aligned;
> };
> @@ -166,7 +171,6 @@ static irqreturn_t max1118_trigger_handler(int irq, void *p)
> struct iio_poll_func *pf = p;
> struct iio_dev *indio_dev = pf->indio_dev;
> struct max1118 *adc = iio_priv(indio_dev);
> - u8 data[16] = { }; /* 2x 8-bit ADC data + padding + 8 bytes timestamp */
> int scan_index;
> int i = 0;
>
> @@ -184,10 +188,10 @@ static irqreturn_t max1118_trigger_handler(int irq, void *p)
> goto out;
> }
>
> - data[i] = ret;
> + adc->scan.channels[i] = ret;
> i++;
> }
> - iio_push_to_buffers_with_timestamp(indio_dev, data,
> + iio_push_to_buffers_with_timestamp(indio_dev, &adc->scan,
> iio_get_time_ns(indio_dev));
> out:
> mutex_unlock(&adc->lock);
