[PATCH v2] iio: imu: st_lsm6dsx: fix possible lockup during FIFO read

[Silvano Seva <s.seva@4sigma.it>]

Prevent st_lsm6dsx_read_fifo and st_lsm6dsx_read_tagged_fifo functions
from falling in an infinite loop in case pattern_len is equal to zero and
the device FIFO is not empty.

Fixes: 290a6ce11d93 ("iio: imu: add support to lsm6dsx driver")
Fixes: 801a6e0af0c6 ("iio: imu: st_lsm6dsx: add support to LSM6DSO")
Signed-off-by: Silvano Seva <s.seva@4sigma.it>
---

Changes since v1:
* st_lsm6dsx_read_fifo: moved check for zero pattern_len before fifo_len assignment
* st_lsm6dsx_read_fifo: dropped check for zero fifo_len
* added Fixes tags in commit message

 drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
index 0a7cd8c1aa33..8a9d2593576a 100644
--- a/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
+++ b/drivers/iio/imu/st_lsm6dsx/st_lsm6dsx_buffer.c
@@ -392,6 +392,9 @@ int st_lsm6dsx_read_fifo(struct st_lsm6dsx_hw *hw)
 	if (fifo_status & cpu_to_le16(ST_LSM6DSX_FIFO_EMPTY_MASK))
 		return 0;
 
+	if (!pattern_len)
+		pattern_len = ST_LSM6DSX_SAMPLE_SIZE;
+
 	fifo_len = (le16_to_cpu(fifo_status) & fifo_diff_mask) *
 		   ST_LSM6DSX_CHAN_SIZE;
 	fifo_len = (fifo_len / pattern_len) * pattern_len;
@@ -623,6 +626,9 @@ int st_lsm6dsx_read_tagged_fifo(struct st_lsm6dsx_hw *hw)
 	if (!fifo_len)
 		return 0;
 
+	if (!pattern_len)
+		pattern_len = ST_LSM6DSX_TAGGED_SAMPLE_SIZE;
+
 	for (read_len = 0; read_len < fifo_len; read_len += pattern_len) {
 		err = st_lsm6dsx_read_block(hw,
 					    ST_LSM6DSX_REG_FIFO_OUT_TAG_ADDR,
-- 
2.48.1