[v3,13/27] iio:magnetometer:ak8975 Fix alignment and data leak issues.
diff mbox series

Message ID 20200722155103.979802-14-jic23@kernel.org
State New
Headers show
Series
  • IIO: Fused set 1 and 2 of timestamp alignment fixes
Related show

Commit Message

Jonathan Cameron July 22, 2020, 3:50 p.m. UTC
From: Jonathan Cameron <Jonathan.Cameron@huawei.com>

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 as by
coincidence the padding will end up the same, however I consider
it to make the code less fragile and have included it.

Fixes: bc11ca4a0b84 ("iio:magnetometer:ak8975: triggered buffer support")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: Gregor Boirie <gregor.boirie@parrot.com>
Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/magnetometer/ak8975.c | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

Comments

Jonathan Cameron Aug. 9, 2020, 5:30 p.m. UTC | #1
On Wed, 22 Jul 2020 16:50:49 +0100
Jonathan Cameron <jic23@kernel.org> wrote:

> From: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> 
> 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 as by
> coincidence the padding will end up the same, however I consider
> it to make the code less fragile and have included it.
> 
> Fixes: bc11ca4a0b84 ("iio:magnetometer:ak8975: triggered buffer support")
> Reported-by: Lars-Peter Clausen <lars@metafoo.de>
> Cc: Gregor Boirie <gregor.boirie@parrot.com>
> Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> Cc: Linus Walleij <linus.walleij@linaro.org>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Applied and marked for stable.

Thanks,

Jonathan

> ---
>  drivers/iio/magnetometer/ak8975.c | 16 +++++++++++-----
>  1 file changed, 11 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
> index 03d71f796177..623766ff800b 100644
> --- a/drivers/iio/magnetometer/ak8975.c
> +++ b/drivers/iio/magnetometer/ak8975.c
> @@ -366,6 +366,12 @@ struct ak8975_data {
>  	struct iio_mount_matrix orientation;
>  	struct regulator	*vdd;
>  	struct regulator	*vid;
> +
> +	/* Ensure natural alignment of timestamp */
> +	struct {
> +		s16 channels[3];
> +		s64 ts __aligned(8);
> +	} scan;
>  };
>  
>  /* Enable attached power regulator if any. */
> @@ -793,7 +799,6 @@ static void ak8975_fill_buffer(struct iio_dev *indio_dev)
>  	const struct i2c_client *client = data->client;
>  	const struct ak_def *def = data->def;
>  	int ret;
> -	s16 buff[8]; /* 3 x 16 bits axis values + 1 aligned 64 bits timestamp */
>  	__le16 fval[3];
>  
>  	mutex_lock(&data->lock);
> @@ -816,12 +821,13 @@ static void ak8975_fill_buffer(struct iio_dev *indio_dev)
>  	mutex_unlock(&data->lock);
>  
>  	/* Clamp to valid range. */
> -	buff[0] = clamp_t(s16, le16_to_cpu(fval[0]), -def->range, def->range);
> -	buff[1] = clamp_t(s16, le16_to_cpu(fval[1]), -def->range, def->range);
> -	buff[2] = clamp_t(s16, le16_to_cpu(fval[2]), -def->range, def->range);
> +	data->scan.channels[0] = clamp_t(s16, le16_to_cpu(fval[0]), -def->range, def->range);
> +	data->scan.channels[1] = clamp_t(s16, le16_to_cpu(fval[1]), -def->range, def->range);
> +	data->scan.channels[2] = clamp_t(s16, le16_to_cpu(fval[2]), -def->range, def->range);
>  
> -	iio_push_to_buffers_with_timestamp(indio_dev, buff,
> +	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
>  					   iio_get_time_ns(indio_dev));
> +
>  	return;
>  
>  unlock:

Patch
diff mbox series

diff --git a/drivers/iio/magnetometer/ak8975.c b/drivers/iio/magnetometer/ak8975.c
index 03d71f796177..623766ff800b 100644
--- a/drivers/iio/magnetometer/ak8975.c
+++ b/drivers/iio/magnetometer/ak8975.c
@@ -366,6 +366,12 @@  struct ak8975_data {
 	struct iio_mount_matrix orientation;
 	struct regulator	*vdd;
 	struct regulator	*vid;
+
+	/* Ensure natural alignment of timestamp */
+	struct {
+		s16 channels[3];
+		s64 ts __aligned(8);
+	} scan;
 };
 
 /* Enable attached power regulator if any. */
@@ -793,7 +799,6 @@  static void ak8975_fill_buffer(struct iio_dev *indio_dev)
 	const struct i2c_client *client = data->client;
 	const struct ak_def *def = data->def;
 	int ret;
-	s16 buff[8]; /* 3 x 16 bits axis values + 1 aligned 64 bits timestamp */
 	__le16 fval[3];
 
 	mutex_lock(&data->lock);
@@ -816,12 +821,13 @@  static void ak8975_fill_buffer(struct iio_dev *indio_dev)
 	mutex_unlock(&data->lock);
 
 	/* Clamp to valid range. */
-	buff[0] = clamp_t(s16, le16_to_cpu(fval[0]), -def->range, def->range);
-	buff[1] = clamp_t(s16, le16_to_cpu(fval[1]), -def->range, def->range);
-	buff[2] = clamp_t(s16, le16_to_cpu(fval[2]), -def->range, def->range);
+	data->scan.channels[0] = clamp_t(s16, le16_to_cpu(fval[0]), -def->range, def->range);
+	data->scan.channels[1] = clamp_t(s16, le16_to_cpu(fval[1]), -def->range, def->range);
+	data->scan.channels[2] = clamp_t(s16, le16_to_cpu(fval[2]), -def->range, def->range);
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buff,
+	iio_push_to_buffers_with_timestamp(indio_dev, &data->scan,
 					   iio_get_time_ns(indio_dev));
+
 	return;
 
 unlock: