From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, Lars-Peter Clausen <lars@metafoo.de>,
        Stable@vger.kernel.org,
        Jonathan Cameron <Jonathan.Cameron@huawei.com>
Subject: [PATCH 4.4 32/37] iio: mma8452: Fix trigger reference couting
Date:   Mon, 13 Dec 2021 10:30:10 +0100
Message-Id: <20211213092926.428930075@linuxfoundation.org>
In-Reply-To: <20211213092925.380184671@linuxfoundation.org>
References: <20211213092925.380184671@linuxfoundation.org>
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From: Lars-Peter Clausen <lars@metafoo.de>

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@metafoo.de>
Link: https://lore.kernel.org/r/20211024092700.6844-1-lars@metafoo.de
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 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
@@ -1011,7 +1011,7 @@ static int mma8452_trigger_setup(struct
 	if (ret)
 		return ret;
 
-	indio_dev->trig = trig;
+	indio_dev->trig = iio_trigger_get(trig);
 
 	return 0;
 }