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[5.6,25/41] iio:chemical:pms7003: Fix timestamp alignment and prevent data leak.

Message ID 20200609174114.531191397@linuxfoundation.org
State Superseded
Headers show
Series None | expand

Commit Message

Greg KH June 9, 2020, 5:45 p.m. UTC 
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>


commit 13e945631c2ffb946c0af342812a3cd39227de6e 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 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 with alignment
explicitly requested.  This data is allocated with kzalloc so no
data can leak appart from previous readings.

Fixes: a1d642266c14 ("iio: chemical: add support for Plantower PMS7003 sensor")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

Cc: <Stable@vger.kernel.org>
Acked-by: Tomasz Duszynski <tomasz.duszynski@octakon.com>

Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>


---
 drivers/iio/chemical/pms7003.c |   17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)
diff mbox series

Patch

--- a/drivers/iio/chemical/pms7003.c
+++ b/drivers/iio/chemical/pms7003.c
@@ -73,6 +73,11 @@  struct pms7003_state {
 	struct pms7003_frame frame;
 	struct completion frame_ready;
 	struct mutex lock; /* must be held whenever state gets touched */
+	/* Used to construct scan to push to the IIO buffer */
+	struct {
+		u16 data[3]; /* PM1, PM2P5, PM10 */
+		s64 ts;
+	} scan;
 };
 
 static int pms7003_do_cmd(struct pms7003_state *state, enum pms7003_cmd cmd)
@@ -104,7 +109,6 @@  static irqreturn_t pms7003_trigger_handl
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct pms7003_state *state = iio_priv(indio_dev);
 	struct pms7003_frame *frame = &state->frame;
-	u16 data[3 + 1 + 4]; /* PM1, PM2P5, PM10, padding, timestamp */
 	int ret;
 
 	mutex_lock(&state->lock);
@@ -114,12 +118,15 @@  static irqreturn_t pms7003_trigger_handl
 		goto err;
 	}
 
-	data[PM1] = pms7003_get_pm(frame->data + PMS7003_PM1_OFFSET);
-	data[PM2P5] = pms7003_get_pm(frame->data + PMS7003_PM2P5_OFFSET);
-	data[PM10] = pms7003_get_pm(frame->data + PMS7003_PM10_OFFSET);
+	state->scan.data[PM1] =
+		pms7003_get_pm(frame->data + PMS7003_PM1_OFFSET);
+	state->scan.data[PM2P5] =
+		pms7003_get_pm(frame->data + PMS7003_PM2P5_OFFSET);
+	state->scan.data[PM10] =
+		pms7003_get_pm(frame->data + PMS7003_PM10_OFFSET);
 	mutex_unlock(&state->lock);
 
-	iio_push_to_buffers_with_timestamp(indio_dev, data,
+	iio_push_to_buffers_with_timestamp(indio_dev, &state->scan,
 					   iio_get_time_ns(indio_dev));
 err:
 	iio_trigger_notify_done(indio_dev->trig);