On Wed, 22 Jul 2020 16:50:52 +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 an array of suitable structures in the iio_priv() data.
>
> This data is allocated with kzalloc so no data can leak apart from
> previous readings.
>
> For the tagged path the data is aligned by using __aligned(8) for
> the buffer on the stack.
>
> There has been a lot of churn in this driver, so likely backports
> may be needed for stable.
>
> Fixes: 290a6ce11d93 ("iio: imu: add support to lsm6dsx driver")
> Reported-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
> Cc: Lorenzo Bianconi <lorenzo.bianconi83@xxxxxxxxx>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
As Lorenzo expressed he was happy with the approach in v1, I've applied
this with an additional comment added for the aligned u8 buffer to
explain what is going on there.
Applied to the togreg branch of iio.git and marked for stable.
It's late enough in the cycle that this can wait for the next merge window.
Thanks,
Jonathan
> ---
> drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h | 6 ++++
> .../iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c | 36 ++++++++++---------
> 2 files changed, 26 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> index d80ba2e688ed..9275346a9cc1 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx.h
> @@ -383,6 +383,7 @@ struct st_lsm6dsx_sensor {
> * @iio_devs: Pointers to acc/gyro iio_dev instances.
> * @settings: Pointer to the specific sensor settings in use.
> * @orientation: sensor chip orientation relative to main hardware.
> + * @scan: Temporary buffers used to align data before iio_push_to_buffers()
> */
> struct st_lsm6dsx_hw {
> struct device *dev;
> @@ -411,6 +412,11 @@ struct st_lsm6dsx_hw {
> const struct st_lsm6dsx_settings *settings;
>
> struct iio_mount_matrix orientation;
> + /* Ensure natural alignment of buffer elements */
> + struct {
> + __le16 channels[3];
> + s64 ts __aligned(8);
> + } scan[3];
> };
>
> static __maybe_unused const struct iio_event_spec st_lsm6dsx_event = {
> diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> index 7de10bd636ea..9e0404e3581d 100644
> --- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> +++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
> @@ -353,9 +353,6 @@ int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
> int err, sip, acc_sip, gyro_sip, ts_sip, ext_sip, read_len, offset;
> u16 fifo_len, pattern_len = hw->sip * ST_LSM6DSX_SAMPLE_SIZE;
> u16 fifo_diff_mask = hw->settings->fifo_ops.fifo_diff.mask;
> - u8 gyro_buff[ST_LSM6DSX_IIO_BUFF_SIZE];
> - u8 acc_buff[ST_LSM6DSX_IIO_BUFF_SIZE];
> - u8 ext_buff[ST_LSM6DSX_IIO_BUFF_SIZE];
> bool reset_ts = false;
> __le16 fifo_status;
> s64 ts = 0;
> @@ -416,19 +413,22 @@ int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
>
> while (acc_sip > 0 || gyro_sip > 0 || ext_sip > 0) {
> if (gyro_sip > 0 && !(sip % gyro_sensor->decimator)) {
> - memcpy(gyro_buff, &hw->buff[offset],
> - ST_LSM6DSX_SAMPLE_SIZE);
> - offset += ST_LSM6DSX_SAMPLE_SIZE;
> + memcpy(hw->scan[ST_LSM6DSX_ID_GYRO].channels,
> + &hw->buff[offset],
> + sizeof(hw->scan[ST_LSM6DSX_ID_GYRO].channels));
> + offset += sizeof(hw->scan[ST_LSM6DSX_ID_GYRO].channels);
> }
> if (acc_sip > 0 && !(sip % acc_sensor->decimator)) {
> - memcpy(acc_buff, &hw->buff[offset],
> - ST_LSM6DSX_SAMPLE_SIZE);
> - offset += ST_LSM6DSX_SAMPLE_SIZE;
> + memcpy(hw->scan[ST_LSM6DSX_ID_ACC].channels,
> + &hw->buff[offset],
> + sizeof(hw->scan[ST_LSM6DSX_ID_ACC].channels));
> + offset += sizeof(hw->scan[ST_LSM6DSX_ID_ACC].channels);
> }
> if (ext_sip > 0 && !(sip % ext_sensor->decimator)) {
> - memcpy(ext_buff, &hw->buff[offset],
> - ST_LSM6DSX_SAMPLE_SIZE);
> - offset += ST_LSM6DSX_SAMPLE_SIZE;
> + memcpy(hw->scan[ST_LSM6DSX_ID_EXT0].channels,
> + &hw->buff[offset],
> + sizeof(hw->scan[ST_LSM6DSX_ID_EXT0].channels));
> + offset += sizeof(hw->scan[ST_LSM6DSX_ID_EXT0].channels);
> }
>
> if (ts_sip-- > 0) {
> @@ -458,19 +458,22 @@ int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
> if (gyro_sip > 0 && !(sip % gyro_sensor->decimator)) {
> iio_push_to_buffers_with_timestamp(
> hw->iio_devs[ST_LSM6DSX_ID_GYRO],
> - gyro_buff, gyro_sensor->ts_ref + ts);
> + &hw->scan[ST_LSM6DSX_ID_GYRO],
> + gyro_sensor->ts_ref + ts);
> gyro_sip--;
> }
> if (acc_sip > 0 && !(sip % acc_sensor->decimator)) {
> iio_push_to_buffers_with_timestamp(
> hw->iio_devs[ST_LSM6DSX_ID_ACC],
> - acc_buff, acc_sensor->ts_ref + ts);
> + &hw->scan[ST_LSM6DSX_ID_ACC],
> + acc_sensor->ts_ref + ts);
> acc_sip--;
> }
> if (ext_sip > 0 && !(sip % ext_sensor->decimator)) {
> iio_push_to_buffers_with_timestamp(
> hw->iio_devs[ST_LSM6DSX_ID_EXT0],
> - ext_buff, ext_sensor->ts_ref + ts);
> + &hw->scan[ST_LSM6DSX_ID_EXT0],
> + ext_sensor->ts_ref + ts);
> ext_sip--;
> }
> sip++;
> @@ -555,7 +558,8 @@ int st_lsm6dsx_read_tagged_fifo(struct st_lsm6dsx_hw *hw)
> {
> u16 pattern_len = hw->sip * ST_LSM6DSX_TAGGED_SAMPLE_SIZE;
> u16 fifo_len, fifo_diff_mask;
> - u8 iio_buff[ST_LSM6DSX_IIO_BUFF_SIZE], tag;
> + u8 iio_buff[ST_LSM6DSX_IIO_BUFF_SIZE] __aligned(8);
> + u8 tag;
> bool reset_ts = false;
> int i, err, read_len;
> __le16 fifo_status;
