patch "iio:humidity:hts221 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:hts221 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 5c49056ad9f3c786f7716da2dd47e4488fc6bd25 Mon Sep 17 00:00:00 2001
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Date: Sun, 7 Jun 2020 16:53:53 +0100
Subject: iio:humidity:hts221 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.

Explicit alignment of ts needed to ensure consistent padding
on all architectures (particularly x86_32 with it's 4 byte alignment
of s64)

Fixes: e4a70e3e7d84 ("iio: humidity: add support to hts221 rh/temp combo device")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Acked-by: Lorenzo Bianconi <lorenzo@kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: <Stable@vger.kernel.org>
---
 drivers/iio/humidity/hts221.h        | 7 +++++--
 drivers/iio/humidity/hts221_buffer.c | 9 +++++----
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/drivers/iio/humidity/hts221.h b/drivers/iio/humidity/hts221.h
index 7d6771f7cf47..b2eb5abeaccd 100644
--- a/drivers/iio/humidity/hts221.h
+++ b/drivers/iio/humidity/hts221.h
@@ -14,8 +14,6 @@
 
 #include <linux/iio/iio.h>
 
-#define HTS221_DATA_SIZE	2
-
 enum hts221_sensor_type {
 	HTS221_SENSOR_H,
 	HTS221_SENSOR_T,
@@ -39,6 +37,11 @@ struct hts221_hw {
 
 	bool enabled;
 	u8 odr;
+	/* Ensure natural alignment of timestamp */
+	struct {
+		__le16 channels[2];
+		s64 ts __aligned(8);
+	} scan;
 };
 
 extern const struct dev_pm_ops hts221_pm_ops;
diff --git a/drivers/iio/humidity/hts221_buffer.c b/drivers/iio/humidity/hts221_buffer.c
index 9fb3f33614d4..ba7d413d75ba 100644
--- a/drivers/iio/humidity/hts221_buffer.c
+++ b/drivers/iio/humidity/hts221_buffer.c
@@ -160,7 +160,6 @@ static const struct iio_buffer_setup_ops hts221_buffer_ops = {
 
 static irqreturn_t hts221_buffer_handler_thread(int irq, void *p)
 {
-	u8 buffer[ALIGN(2 * HTS221_DATA_SIZE, sizeof(s64)) + sizeof(s64)];
 	struct iio_poll_func *pf = p;
 	struct iio_dev *iio_dev = pf->indio_dev;
 	struct hts221_hw *hw = iio_priv(iio_dev);
@@ -170,18 +169,20 @@ static irqreturn_t hts221_buffer_handler_thread(int irq, void *p)
 	/* humidity data */
 	ch = &iio_dev->channels[HTS221_SENSOR_H];
 	err = regmap_bulk_read(hw->regmap, ch->address,
-			       buffer, HTS221_DATA_SIZE);
+			       &hw->scan.channels[0],
+			       sizeof(hw->scan.channels[0]));
 	if (err < 0)
 		goto out;
 
 	/* temperature data */
 	ch = &iio_dev->channels[HTS221_SENSOR_T];
 	err = regmap_bulk_read(hw->regmap, ch->address,
-			       buffer + HTS221_DATA_SIZE, HTS221_DATA_SIZE);
+			       &hw->scan.channels[1],
+			       sizeof(hw->scan.channels[1]));
 	if (err < 0)
 		goto out;
 
-	iio_push_to_buffers_with_timestamp(iio_dev, buffer,
+	iio_push_to_buffers_with_timestamp(iio_dev, &hw->scan,
 					   iio_get_time_ns(iio_dev));
 
 out:
-- 
2.27.0