[PATCH] iio: adis_buffer: Fix out-of-bounds memory access

[PATCH] iio: adis_buffer: Fix out-of-bounds memory access

[Lars-Peter Clausen]

The SPI tx and rx buffers are both supposed to be scan_bytes amount of
bytes large and a common allocation is used to allocate both buffers. This
puts the beginning of the tx buffer scan_bytes bytes after the rx buffer.
The initialization of the tx buffer pointer is done adding scan_bytes to
the beginning of the rx buffer, but since the rx buffer is of type __be16
this will actually add two times as much and the tx buffer ends up pointing
after the allocated buffer.

Fix this by using scan_count, which is scan_bytes / 2, instead of
scan_bytes when initializing the tx buffer pointer.

Fixes: aacff892cbd5 ("staging:iio:adis: Preallocate transfer message")
Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
---
Apologies if you got this twice, forgot the mailinglist on the first try.
---
 drivers/iio/imu/adis_buffer.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iio/imu/adis_buffer.c b/drivers/iio/imu/adis_buffer.c
index cb32b59..36607d5 100644
--- a/drivers/iio/imu/adis_buffer.c
+++ b/drivers/iio/imu/adis_buffer.c
@@ -43,7 +43,7 @@ int adis_update_scan_mode(struct iio_dev *indio_dev,
 		return -ENOMEM;
 
 	rx = adis->buffer;
-	tx = rx + indio_dev->scan_bytes;
+	tx = rx + scan_count;
 
 	spi_message_init(&adis->msg);
 
-- 
2.1.4

Re: [PATCH] iio: adis_buffer: Fix out-of-bounds memory access

[Jonathan Cameron]

On 27/11/15 13:55, Lars-Peter Clausen wrote:
> The SPI tx and rx buffers are both supposed to be scan_bytes amount of
> bytes large and a common allocation is used to allocate both buffers. This
> puts the beginning of the tx buffer scan_bytes bytes after the rx buffer.
> The initialization of the tx buffer pointer is done adding scan_bytes to
> the beginning of the rx buffer, but since the rx buffer is of type __be16
> this will actually add two times as much and the tx buffer ends up pointing
> after the allocated buffer.
> 
> Fix this by using scan_count, which is scan_bytes / 2, instead of
> scan_bytes when initializing the tx buffer pointer.
> 
> Fixes: aacff892cbd5 ("staging:iio:adis: Preallocate transfer message")
> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de>
Applied to my local fixes branch - will push out once Greg has caught
up with last pull request - don't want to muddy the waters!

Jonathan
> ---
> Apologies if you got this twice, forgot the mailinglist on the first try.
> ---
>  drivers/iio/imu/adis_buffer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/iio/imu/adis_buffer.c b/drivers/iio/imu/adis_buffer.c
> index cb32b59..36607d5 100644
> --- a/drivers/iio/imu/adis_buffer.c
> +++ b/drivers/iio/imu/adis_buffer.c
> @@ -43,7 +43,7 @@ int adis_update_scan_mode(struct iio_dev *indio_dev,
>  		return -ENOMEM;
>  
>  	rx = adis->buffer;
> -	tx = rx + indio_dev->scan_bytes;
> +	tx = rx + scan_count;
>  
>  	spi_message_init(&adis->msg);
>  
>