patch "iio:pressure:ms5611 Fix buffer element alignment" added to staging-linus

patch "iio:pressure:ms5611 Fix buffer element alignment" added to staging-linus

[gregkh]

This is a note to let you know that I've just added the patch titled

    iio:pressure:ms5611 Fix buffer element alignment

to my staging git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
in the staging-linus branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will hopefully also be merged in Linus's tree for the
next -rc kernel release.

If you have any questions about this process, please let me know.


From 8db4afe163bbdd93dca6fcefbb831ef12ecc6b4d Mon Sep 17 00:00:00 2001
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Date: Sun, 7 Jun 2020 16:53:57 +0100
Subject: iio:pressure:ms5611 Fix buffer element alignment

One of a class of bugs pointed out by Lars in a recent review.
iio_push_to_buffers_with_timestamp assumes the buffer used is aligned
to the size of the timestamp (8 bytes).  This is not guaranteed in
this driver which uses an array of smaller elements on the stack.
Here there is no data leak possibility so use an explicit structure
on the stack to ensure alignment and nice readable fashion.

The forced alignment of ts isn't strictly necessary in this driver
as the padding will be correct anyway (there isn't any).  However
it is probably less fragile to have it there and it acts as
documentation of the requirement.

Fixes: 713bbb4efb9dc ("iio: pressure: ms5611: Add triggered buffer support")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Acked-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>
Cc: <Stable@vger.kernel.org>
---
 drivers/iio/pressure/ms5611_core.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/pressure/ms5611_core.c b/drivers/iio/pressure/ms5611_core.c
index 2f598ad91621..f5db9fa086f3 100644
--- a/drivers/iio/pressure/ms5611_core.c
+++ b/drivers/iio/pressure/ms5611_core.c
@@ -212,16 +212,21 @@ static irqreturn_t ms5611_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct ms5611_state *st = iio_priv(indio_dev);
-	s32 buf[4]; /* s32 (pressure) + s32 (temp) + 2 * s32 (timestamp) */
+	/* Ensure buffer elements are naturally aligned */
+	struct {
+		s32 channels[2];
+		s64 ts __aligned(8);
+	} scan;
 	int ret;
 
 	mutex_lock(&st->lock);
-	ret = ms5611_read_temp_and_pressure(indio_dev, &buf[1], &buf[0]);
+	ret = ms5611_read_temp_and_pressure(indio_dev, &scan.channels[1],
+					    &scan.channels[0]);
 	mutex_unlock(&st->lock);
 	if (ret < 0)
 		goto err;
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buf,
+	iio_push_to_buffers_with_timestamp(indio_dev, &scan,
 					   iio_get_time_ns(indio_dev));
 
 err:
-- 
2.27.0