FAILED: patch "[PATCH] iio:magnetometer:mag3110: Fix alignment and data leak issues." failed to apply to 4.14-stable tree

The patch below does not apply to the 4.14-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 89deb1334252ea4a8491d47654811e28b0790364 Mon Sep 17 00:00:00 2001
From: Jonathan Cameron <[email protected]>
Date: Sun, 20 Sep 2020 12:27:37 +0100
Subject: [PATCH] iio:magnetometer:mag3110: 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.

The explicit alignment of ts is not necessary in this case but does make the code slightly less fragile so I have included it.

index 838b13c8bb3d..c96415a1aead 100644
@@ -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 temperature;
+		s64 ts __aligned(8);
+	} 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.temperature = 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:

Hi Greg,

Here is the backport, will also apply to 4.9-stable.

--
Regards
Sudip

From 35a03dab47f3edb209085833bc20982bc9fd1a4b Mon Sep 17 00:00:00 2001
From: Jonathan Cameron <[email protected]>
Date: Sun, 20 Sep 2020 12:27:37 +0100
Subject: [PATCH] iio:magnetometer:mag3110: Fix alignment and data leak issues.

commit 89deb1334252ea4a8491d47654811e28b0790364 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.
This data is allocated with kzalloc() so no data can leak apart from previous readings.

The explicit alignment of ts is not necessary in this case but does make the code slightly less fragile so I have included it.

---
 drivers/iio/magnetometer/mag3110.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

index dad8d57f7402..974e141c0dc0 100644
@@ -52,6 +52,12 @@ struct mag3110_data {
 	struct i2c_client *client;
 	struct mutex lock;
 	u8 ctrl_reg1;
+	/* Ensure natural alignment of timestamp */
+	struct {
+		__be16 channels[3];
+		u8 temperature;
+		s64 ts __aligned(8);
+	} scan;
 };
 
 static int mag3110_request(struct mag3110_data *data)

@@ -262,10 +268,9 @@ 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;
 

@@ -274,10 +279,10 @@ static irqreturn_t mag3110_trigger_handler(int irq, void *p)
 			MAG3110_DIE_TEMP);
 		if (ret < 0)
 			goto done;
-		buffer[6] = ret;
+		data->scan.temperature = 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:

2.11.0