rsi: check length before USB read/write register

These checks are required. Otherwise we may end up getting
memory corruption if invalid length is passed.

Fixes: b97e9b94ad ("rsi: Add new host interface operations")
Signed-off-by: Amitkumar Karwar <amit.karwar@redpinesignals.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>

drivers/net/wireless/rsi/rsi_91x_usb.c

@@ -166,6 +166,9 @@ static int rsi_usb_reg_read(struct usb_device *usbdev,
 	if (!buf)
 		return status;
 
+	if (len > RSI_USB_CTRL_BUF_SIZE)
+		return -EINVAL;
+
 	status = usb_control_msg(usbdev,
 				 usb_rcvctrlpipe(usbdev, 0),
 				 USB_VENDOR_REGISTER_READ,
@@ -208,6 +211,9 @@ static int rsi_usb_reg_write(struct usb_device *usbdev,
 	if (!usb_reg_buf)
 		return status;
 
+	if (len > RSI_USB_CTRL_BUF_SIZE)
+		return -EINVAL;
+
 	usb_reg_buf[0] = (value & 0x00ff);
 	usb_reg_buf[1] = (value & 0xff00) >> 8;
 	usb_reg_buf[2] = 0x0;