[PATCH v2] iio: imu: st_lsm6dsx: Fix an array overflow in st_lsm6dsx_set_odr()

[Teng Qi]

The length of hw->settings->odr_table is 2 and ref_sensor->id is an enum
variable whose value is between 0 and 5.
However, the value ST_LSM6DSX_ID_MAX (i.e. 5) is not catched properly in
 switch (sensor->id) {

If ref_sensor->id is ST_LSM6DSX_ID_MAX, an array overflow will ocurrs in
function st_lsm6dsx_check_odr():
  odr_table = &sensor->hw->settings->odr_table[sensor->id];

and in function st_lsm6dsx_set_odr():
  reg = &hw->settings->odr_table[ref_sensor->id].reg;

To fix this array overflow, handle ST_LSM6DSX_ID_GYRO explicitly and 
return -EINVAL for the default case.

Reported-by: TOTE Robot <oslab@xxxxxxxxxxxxxxx>
Signed-off-by: Teng Qi <starmiku1207184332@xxxxxxxxx>

---
v2:
* explicitly handle ST_LSM6DSX_ID_GYRO and return -EINVAL for the default
case instead of adding an if statement behind the switch statement.
  Thank Lars-Peter Clausen for helpful and friendly advice.

---
 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
index db45f1fc0b81..8dbf744c5651 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_core.c
@@ -1279,6 +1279,8 @@ st_lsm6dsx_set_odr(struct st_lsm6dsx_sensor *sensor, u32 req_odr)
 	int err;
 
 	switch (sensor->id) {
+	case ST_LSM6DSX_ID_GYRO:
+		break;
 	case ST_LSM6DSX_ID_EXT0:
 	case ST_LSM6DSX_ID_EXT1:
 	case ST_LSM6DSX_ID_EXT2:
@@ -1304,8 +1306,8 @@ st_lsm6dsx_set_odr(struct st_lsm6dsx_sensor *sensor, u32 req_odr)
 		}
 		break;
 	}
-	default:
-		break;
+	default: /* should never occur */
+		return -EINVAL;
 	}
 
 	if (req_odr > 0) {
-- 
2.25.1