[PATCH v2 2/3] iio: imu: st_lsm6dsx: Set buffer sampling frequency for accelerometer only

[Francesco Lavra <flavra@baylibre.com>]

The st_lsm6dsx_hwfifo_odr_store() function, which is called when userspace
writes the buffer sampling frequency sysfs attribute, calls
st_lsm6dsx_check_odr(), which accesses the odr_table array at index
`sensor->id`; since this array is only 2 entries long, an access for any
sensor type other than accelerometer or gyroscope is an out-of-bounds
access.

To prevent userspace from triggering an out-of-bounds array access, and to
support the only use case for which FIFO sampling frequency values
different from the sensor sampling frequency may be needed (which is for
keeping FIFO data rate low while sampling acceleration data at high rates
for accurate event detection), do not create the buffer sampling frequency
attribute for sensor types other than the accelerometer.

Fixes: 6b648a36c200 ("iio: imu: st_lsm6dsx: Decouple sensor ODR from FIFO batch data rate")
Signed-off-by: Francesco Lavra <flavra@baylibre.com>
---
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
index 1ee2fc5f5f1f..cde29b2e6f34 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
@@ -862,12 +862,21 @@ int st_lsm6dsx_fifo_setup(struct st_lsm6dsx_hw *hw)
 	int i, ret;
 
 	for (i = 0; i < ST_LSM6DSX_ID_MAX; i++) {
+		const struct iio_dev_attr **attrs;
+
 		if (!hw->iio_devs[i])
 			continue;
 
+		/*
+		 * For the accelerometer, allow setting FIFO sampling frequency
+		 * values different from the sensor sampling frequency, which
+		 * may be needed to keep FIFO data rate low while sampling
+		 * acceleration data at high rates for accurate event detection.
+		 */
+		attrs = (i == ST_LSM6DSX_ID_ACC) ? st_lsm6dsx_buffer_attrs : NULL;
 		ret = devm_iio_kfifo_buffer_setup_ext(hw->dev, hw->iio_devs[i],
 						      &st_lsm6dsx_buffer_ops,
-						      st_lsm6dsx_buffer_attrs);
+						      attrs);
 		if (ret)
 			return ret;
 	}
-- 
2.39.5