ieee802154: atusb: do not use the stack for buffers to make them DMA able

From 4.9 we should really avoid using the stack here as this will not be DMA
able on various platforms. This changes the buffers already being present in
time of 4.9 being released. This should go into stable as well.
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Cc: stable@vger.kernel.org
Signed-off-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

drivers/net/ieee802154/atusb.c

@@ -117,13 +117,26 @@ static int atusb_read_reg(struct atusb *atusb, uint8_t reg)
 {
 	struct usb_device *usb_dev = atusb->usb_dev;
 	int ret;
+	uint8_t *buffer;
 	uint8_t value;
 
+	buffer = kmalloc(1, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
 	dev_dbg(&usb_dev->dev, "atusb: reg = 0x%x\n", reg);
 	ret = atusb_control_msg(atusb, usb_rcvctrlpipe(usb_dev, 0),
 				ATUSB_REG_READ, ATUSB_REQ_FROM_DEV,
-				0, reg, &value, 1, 1000);
-	return ret >= 0 ? value : ret;
+				0, reg, buffer, 1, 1000);
+
+	if (ret >= 0) {
+		value = buffer[0];
+		kfree(buffer);
+		return value;
+	} else {
+		kfree(buffer);
+		return ret;
+	}
 }
 
 static int atusb_write_subreg(struct atusb *atusb, uint8_t reg, uint8_t mask,
@@ -608,9 +621,13 @@ static const struct ieee802154_ops atusb_ops = {
 static int atusb_get_and_show_revision(struct atusb *atusb)
 {
 	struct usb_device *usb_dev = atusb->usb_dev;
-	unsigned char buffer[3];
+	unsigned char *buffer;
 	int ret;
 
+	buffer = kmalloc(3, GFP_KERNEL);
+	if (!buffer)
+		return -ENOMEM;
+
 	/* Get a couple of the ATMega Firmware values */
 	ret = atusb_control_msg(atusb, usb_rcvctrlpipe(usb_dev, 0),
 				ATUSB_ID, ATUSB_REQ_FROM_DEV, 0, 0,
@@ -631,15 +648,20 @@ static int atusb_get_and_show_revision(struct atusb *atusb)
 		dev_info(&usb_dev->dev, "Please update to version 0.2 or newer");
 	}
 
+	kfree(buffer);
 	return ret;
 }
 
 static int atusb_get_and_show_build(struct atusb *atusb)
 {
 	struct usb_device *usb_dev = atusb->usb_dev;
-	char build[ATUSB_BUILD_SIZE + 1];
+	char *build;
 	int ret;
 
+	build = kmalloc(ATUSB_BUILD_SIZE + 1, GFP_KERNEL);
+	if (!build)
+		return -ENOMEM;
+
 	ret = atusb_control_msg(atusb, usb_rcvctrlpipe(usb_dev, 0),
 				ATUSB_BUILD, ATUSB_REQ_FROM_DEV, 0, 0,
 				build, ATUSB_BUILD_SIZE, 1000);
@@ -648,6 +670,7 @@ static int atusb_get_and_show_build(struct atusb *atusb)
 		dev_info(&usb_dev->dev, "Firmware: build %s\n", build);
 	}
 
+	kfree(build);
 	return ret;
 }