iio: mma8452: Fix trigger reference couting

The mma8452 driver directly assigns a trigger to the struct iio_dev. The
IIO core when done using this trigger will call `iio_trigger_put()` to drop
the reference count by 1.

Without the matching `iio_trigger_get()` in the driver the reference count
can reach 0 too early, the trigger gets freed while still in use and a
use-after-free occurs.

Fix this by getting a reference to the trigger before assigning it to the
IIO device.

Fixes: ae6d9ce ("iio: mma8452: Add support for interrupt driven triggers.")
Signed-off-by: Lars-Peter Clausen <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Cc: <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>

Author: larsclausen

drivers/iio/accel/mma8452.c

@@ -1470,7 +1470,7 @@ static int mma8452_trigger_setup(struct iio_dev *indio_dev)
 	if (ret)
 		return ret;
 
-	indio_dev->trig = trig;
+	indio_dev->trig = iio_trigger_get(trig);
 
 	return 0;
 }