patch "iio:humidity:hdc100x Fix alignment and data leak issues" added to staging-linus

[<gregkh@linuxfoundation.org>]

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

    iio:humidity:hdc100x Fix alignment and data leak issues

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 ea5e7a7bb6205d24371373cd80325db1bc15eded Mon Sep 17 00:00:00 2001
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Date: Sun, 7 Jun 2020 16:53:52 +0100
Subject: iio:humidity:hdc100x Fix alignment and data leak issues

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: 16bf793f86b2 ("iio: humidity: hdc100x: add triggered buffer support for HDC100X")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Matt Ranostay <matt.ranostay@konsulko.com>
Cc: Alison Schofield <amsfield22@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: <Stable@vger.kernel.org>
---
 drivers/iio/humidity/hdc100x.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/humidity/hdc100x.c b/drivers/iio/humidity/hdc100x.c
index 7ecd2ffa3132..665eb7e38293 100644
--- a/drivers/iio/humidity/hdc100x.c
+++ b/drivers/iio/humidity/hdc100x.c
@@ -38,6 +38,11 @@ struct hdc100x_data {
 
 	/* integration time of the sensor */
 	int adc_int_us[2];
+	/* Ensure natural alignment of timestamp */
+	struct {
+		__be16 channels[2];
+		s64 ts __aligned(8);
+	} scan;
 };
 
 /* integration time in us */
@@ -322,7 +327,6 @@ static irqreturn_t hdc100x_trigger_handler(int irq, void *p)
 	struct i2c_client *client = data->client;
 	int delay = data->adc_int_us[0] + data->adc_int_us[1];
 	int ret;
-	s16 buf[8];  /* 2x s16 + padding + 8 byte timestamp */
 
 	/* dual read starts at temp register */
 	mutex_lock(&data->lock);
@@ -333,13 +337,13 @@ static irqreturn_t hdc100x_trigger_handler(int irq, void *p)
 	}
 	usleep_range(delay, delay + 1000);
 
-	ret = i2c_master_recv(client, (u8 *)buf, 4);
+	ret = i2c_master_recv(client, (u8 *)data->scan.channels, 4);
 	if (ret < 0) {
 		dev_err(&client->dev, "cannot read sensor data\n");
 		goto err;
 	}
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buf,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
 					   iio_get_time_ns(indio_dev));
 err:
 	mutex_unlock(&data->lock);
-- 
2.27.0