linux-kernel - [PATCH 4.19 036/133] iio:health:afe4403 Fix timestamp alignment and prevent data leak.

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Message-Id: <20200720152805.462507150@linuxfoundation.org>
Date:   Mon, 20 Jul 2020 17:36:23 +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>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        "Andrew F. Davis" <afd@...com>, Stable@...r.kernel.org
Subject: [PATCH 4.19 036/133] iio:health:afe4403 Fix timestamp alignment and prevent data leak.

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

commit 3f9c6d38797e9903937b007a341dad0c251765d6 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 32 byte array of smaller elements 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
explicitly requested.  This data is allocated with kzalloc so no
data can leak appart from previous readings.

Fixes: eec96d1e2d31 ("iio: health: Add driver for the TI AFE4403 heart monitor")
Reported-by: Lars-Peter Clausen <lars@...afoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Acked-by: Andrew F. Davis <afd@...com>
Cc: <Stable@...r.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/iio/health/afe4403.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

--- a/drivers/iio/health/afe4403.c
+++ b/drivers/iio/health/afe4403.c
@@ -71,6 +71,7 @@ static const struct reg_field afe4403_re
  * @regulator: Pointer to the regulator for the IC
  * @trig: IIO trigger for this device
  * @irq: ADC_RDY line interrupt number
+ * @buffer: Used to construct data layout to push into IIO buffer.
  */
 struct afe4403_data {
 	struct device *dev;
@@ -80,6 +81,8 @@ struct afe4403_data {
 	struct regulator *regulator;
 	struct iio_trigger *trig;
 	int irq;
+	/* Ensure suitable alignment for timestamp */
+	s32 buffer[8] __aligned(8);
 };

 enum afe4403_chan_id {
@@ -317,7 +320,6 @@ static irqreturn_t afe4403_trigger_handl
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct afe4403_data *afe = iio_priv(indio_dev);
 	int ret, bit, i = 0;
-	s32 buffer[8];
 	u8 tx[4] = {AFE440X_CONTROL0, 0x0, 0x0, AFE440X_CONTROL0_READ};
 	u8 rx[3];

@@ -334,9 +336,9 @@ static irqreturn_t afe4403_trigger_handl
 		if (ret)
 			goto err;

-		buffer[i++] = (rx[0] << 16) |
-				(rx[1] << 8) |
-				(rx[2]);
+		afe->buffer[i++] = (rx[0] << 16) |
+				   (rx[1] << 8) |
+				   (rx[2]);
 	}

 	/* Disable reading from the device */
@@ -345,7 +347,8 @@ static irqreturn_t afe4403_trigger_handl
 	if (ret)
 		goto err;

-	iio_push_to_buffers_with_timestamp(indio_dev, buffer, pf->timestamp);
+	iio_push_to_buffers_with_timestamp(indio_dev, afe->buffer,
+					   pf->timestamp);
 err:
 	iio_trigger_notify_done(indio_dev->trig);