[v3,04/27] iio:accel:mma7455: Fix timestamp alignment and prevent data leak.
diff mbox series

Message ID 20200722155103.979802-5-jic23@kernel.org
State New
Headers show
Series
  • IIO: Fused set 1 and 2 of timestamp alignment fixes
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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 a 16 byte u8 array 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
ensured by use of an explicit c structure.  This data is allocated
with kzalloc so no data can leak appart from previous readings.

The force alignment of ts is not strictly necessary in this particularly
case but does make the code less fragile.

Fixes: a84ef0d181d9 ("iio: accel: add Freescale MMA7455L/MMA7456L 3-axis accelerometer driver")
Reported-by: Lars-Peter Clausen <lars@metafoo.de>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
---
 drivers/iio/accel/mma7455_core.c | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

Comments

Jonathan Cameron Aug. 9, 2020, 5:19 p.m. UTC | #1
On Wed, 22 Jul 2020 16:50:40 +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 a 16 byte u8 array 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
> ensured by use of an explicit c structure.  This data is allocated
> with kzalloc so no data can leak appart from previous readings.
> 
> The force alignment of ts is not strictly necessary in this particularly
> case but does make the code less fragile.
> 
> Fixes: a84ef0d181d9 ("iio: accel: add Freescale MMA7455L/MMA7456L 3-axis accelerometer driver")
> Reported-by: Lars-Peter Clausen <lars@metafoo.de>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Applied to the fixes-togreg branch of iio.git and marked for stable.

Thanks,

Jonathan

> ---
>  drivers/iio/accel/mma7455_core.c | 16 ++++++++++++----
>  1 file changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/accel/mma7455_core.c b/drivers/iio/accel/mma7455_core.c
> index 7e99bcb3398d..922bd38ff6ea 100644
> --- a/drivers/iio/accel/mma7455_core.c
> +++ b/drivers/iio/accel/mma7455_core.c
> @@ -52,6 +52,14 @@
>  
>  struct mma7455_data {
>  	struct regmap *regmap;
> +	/*
> +	 * Used to reorganize data.  Will ensure correct alignment of
> +	 * the timestamp if present
> +	 */
> +	struct {
> +		__le16 channels[3];
> +		s64 ts __aligned(8);
> +	} scan;
>  };
>  
>  static int mma7455_drdy(struct mma7455_data *mma7455)
> @@ -82,19 +90,19 @@ static irqreturn_t mma7455_trigger_handler(int irq, void *p)
>  	struct iio_poll_func *pf = p;
>  	struct iio_dev *indio_dev = pf->indio_dev;
>  	struct mma7455_data *mma7455 = iio_priv(indio_dev);
> -	u8 buf[16]; /* 3 x 16-bit channels + padding + ts */
>  	int ret;
>  
>  	ret = mma7455_drdy(mma7455);
>  	if (ret)
>  		goto done;
>  
> -	ret = regmap_bulk_read(mma7455->regmap, MMA7455_REG_XOUTL, buf,
> -			       sizeof(__le16) * 3);
> +	ret = regmap_bulk_read(mma7455->regmap, MMA7455_REG_XOUTL,
> +			       mma7455->scan.channels,
> +			       sizeof(mma7455->scan.channels));
>  	if (ret)
>  		goto done;
>  
> -	iio_push_to_buffers_with_timestamp(indio_dev, buf,
> +	iio_push_to_buffers_with_timestamp(indio_dev, &mma7455->scan,
>  					   iio_get_time_ns(indio_dev));
>  
>  done:

Patch
diff mbox series

diff --git a/drivers/iio/accel/mma7455_core.c b/drivers/iio/accel/mma7455_core.c
index 7e99bcb3398d..922bd38ff6ea 100644
--- a/drivers/iio/accel/mma7455_core.c
+++ b/drivers/iio/accel/mma7455_core.c
@@ -52,6 +52,14 @@ 
 
 struct mma7455_data {
 	struct regmap *regmap;
+	/*
+	 * Used to reorganize data.  Will ensure correct alignment of
+	 * the timestamp if present
+	 */
+	struct {
+		__le16 channels[3];
+		s64 ts __aligned(8);
+	} scan;
 };
 
 static int mma7455_drdy(struct mma7455_data *mma7455)
@@ -82,19 +90,19 @@  static irqreturn_t mma7455_trigger_handler(int irq, void *p)
 	struct iio_poll_func *pf = p;
 	struct iio_dev *indio_dev = pf->indio_dev;
 	struct mma7455_data *mma7455 = iio_priv(indio_dev);
-	u8 buf[16]; /* 3 x 16-bit channels + padding + ts */
 	int ret;
 
 	ret = mma7455_drdy(mma7455);
 	if (ret)
 		goto done;
 
-	ret = regmap_bulk_read(mma7455->regmap, MMA7455_REG_XOUTL, buf,
-			       sizeof(__le16) * 3);
+	ret = regmap_bulk_read(mma7455->regmap, MMA7455_REG_XOUTL,
+			       mma7455->scan.channels,
+			       sizeof(mma7455->scan.channels));
 	if (ret)
 		goto done;
 
-	iio_push_to_buffers_with_timestamp(indio_dev, buf,
+	iio_push_to_buffers_with_timestamp(indio_dev, &mma7455->scan,
 					   iio_get_time_ns(indio_dev));
 
 done: