iio: imu: adis16400: release allocated memory on failure

CVE-2019-19060

In adis_update_scan_mode, if allocation for adis->buffer fails,
previously allocated adis->xfer needs to be released.
Signed-off-by: Navid Emamdoost <navid.emamdoost@gmail.com>
Reviewed-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
(backported from commit ab612b1d)
[PHLin: context adjustment]
Signed-off-by: Po-Hsu Lin <po-hsu.lin@canonical.com>
Acked-by: Benjamin M Romer <benjamin.romer@canonical.com>
Acked-by: Sultan Alsawaf <sultan.alsawaf@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

drivers/iio/imu/adis_buffer.c

@@ -39,8 +39,11 @@ int adis_update_scan_mode(struct iio_dev *indio_dev,
 		return -ENOMEM;
 
 	adis->buffer = kzalloc(indio_dev->scan_bytes * 2, GFP_KERNEL);
-	if (!adis->buffer)
+	if (!adis->buffer) {
+		kfree(adis->xfer);
+		adis->xfer = NULL;
 		return -ENOMEM;
+	}
 
 	rx = adis->buffer;
 	tx = rx + scan_count;