[08/25] iio:magnetometer:mag3110 Fix alignment and data leak issues.

Commit Message

Jonathan Cameron May 25, 2020, 5:06 p.m. UTC

From: Jonathan Cameron <[e-mail]>

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.
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.
This data is allocated with kzalloc so no data can leak apart from
previous readings.

Fixes: 39631b5f9584 ("iio: Add Freescale mag3110 magnetometer driver")
Reported-by: Lars-Peter Clausen <[e-mail]>
Signed-off-by: Jonathan Cameron <[e-mail]>
---
 drivers/iio/magnetometer/mag3110.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

Patch

diff --git a/drivers/iio/magnetometer/mag3110.c b/drivers/iio/magnetometer/mag3110.c
index fb16cfdd6fa6..17cd613c21c9 100644
--- a/drivers/iio/magnetometer/mag3110.c
+++ b/drivers/iio/magnetometer/mag3110.c
@@ -56,6 +56,12 @@  struct mag3110_data {
 	int sleep_val;
 	struct regulator *vdd_reg;
 	struct regulator *vddio_reg;
+	/* Ensure natural alignment of timestamp */
+	struct {
+		__be16 channels[3];
+		u8 temp;
+		s64 ts;
+	} scan;
 };
 
 static int mag3110_request(struct mag3110_data *data)
@@ -387,10 +393,9 @@  static irqreturn_t mag3110_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct mag3110_data *data = iio_priv(indio_dev);
-	u8 buffer[16]; /* 3 16-bit channels + 1 byte temp + padding + ts */
 	int ret;
 
-	ret = mag3110_read(data, (__be16 *) buffer);
+	ret = mag3110_read(data, data->scan.channels);
 	if (ret < 0)
 		goto done;
 
@@ -399,10 +404,10 @@  static irqreturn_t mag3110_trigger_handler(int irq, void *p)
 			MAG3110_DIE_TEMP);
 		if (ret < 0)
 			goto done;
-		buffer[6] = ret;
+		data->scan.temp = ret;
 	}
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buffer,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
 		iio_get_time_ns(indio_dev));
 
 done: