[PATCH 5.15 147/171] iio: mma8452: Fix trigger reference couting

[Greg Kroah-Hartman]

From: Lars-Peter Clausen <lars@xxxxxxxxxx>

commit cd0082235783f814241a1c9483fb89e405f4f892 upstream.

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: ae6d9ce05691 ("iio: mma8452: Add support for interrupt driven triggers.")
Signed-off-by: Lars-Peter Clausen <lars@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20211024092700.6844-1-lars@xxxxxxxxxx
Cc: <Stable@xxxxxxxxxxxxxxx>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@xxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/iio/accel/mma8452.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/iio/accel/mma8452.c
+++ b/drivers/iio/accel/mma8452.c
@@ -1470,7 +1470,7 @@ static int mma8452_trigger_setup(struct
 	if (ret)
 		return ret;
 
-	indio_dev->trig = trig;
+	indio_dev->trig = iio_trigger_get(trig);
 
 	return 0;
 }