linux-kernel - [PATCH 5.8 113/177] iio:proximity:mb1232: Fix timestamp alignment and prevent data leak.

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Date:   Tue, 15 Sep 2020 16:13:04 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Lars-Peter Clausen <lars@...afoo.de>,
        Andreas Klinger <ak@...klinger.de>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Stable@...r.kernel.org, Andy Shevchenko <andy.shevchenko@...il.com>
Subject: [PATCH 5.8 113/177] iio:proximity:mb1232: Fix timestamp alignment and prevent data leak.

From: Jonathan Cameron <Jonathan.Cameron@...wei.com>

commit f60e8bb84282b8e633956cfe74b4f0d64ca73cec upstream.

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 a 16 byte s16 array on the stack   As Lars also noted
this anti pattern can involve a leak of data to userspace and that
indeed can happen here.  We close both issues by moving to
a suitable structure in the iio_priv() data with alignment
ensured by use of an explicit c structure.  This data is allocated
with kzalloc so no data can leak appart from previous readings.

In this case the forced alignment of the ts is necessary to ensure
correct padding on x86_32 where the s64 would only be 4 byte aligned.

Fixes: 16b05261537e ("mb1232.c: add distance iio sensor with i2c")
Reported-by: Lars-Peter Clausen <lars@...afoo.de>
Cc: Andreas Klinger <ak@...klinger.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Cc: <Stable@...r.kernel.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/iio/proximity/mb1232.c |   17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

--- a/drivers/iio/proximity/mb1232.c
+++ b/drivers/iio/proximity/mb1232.c
@@ -40,6 +40,11 @@ struct mb1232_data {
 	 */
 	struct completion	ranging;
 	int			irqnr;
+	/* Ensure correct alignment of data to push to IIO buffer */
+	struct {
+		s16 distance;
+		s64 ts __aligned(8);
+	} scan;
 };
 
 static irqreturn_t mb1232_handle_irq(int irq, void *dev_id)
@@ -113,17 +118,13 @@ static irqreturn_t mb1232_trigger_handle
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct mb1232_data *data = iio_priv(indio_dev);
-	/*
-	 * triggered buffer
-	 * 16-bit channel + 48-bit padding + 64-bit timestamp
-	 */
-	s16 buffer[8] = { 0 };
 
-	buffer[0] = mb1232_read_distance(data);
-	if (buffer[0] < 0)
+	data->scan.distance = mb1232_read_distance(data);
+	if (data->scan.distance < 0)
 		goto err;
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buffer, pf->timestamp);
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
+					   pf->timestamp);
 
 err:
 	iio_trigger_notify_done(indio_dev->trig);