Merge tag 'usb-serial-5.8-rc6' of https://git.kernel.org/pub/scm/linu…

…x/kernel/git/johan/usb-serial into usb-linus

Johan writes:

USB-serial fixes for 5.8-rc6

Here's a fix for 5.8 addressing a long-standing bug in iuu_phoenix.

* tag 'usb-serial-5.8-rc6' of https://git.kernel.org/pub/scm/linux/kernel/git/johan/usb-serial:
  USB: serial: iuu_phoenix: fix memory corruption

drivers/usb/serial/iuu_phoenix.c

@@ -697,14 +697,16 @@ static int iuu_uart_write(struct tty_struct *tty, struct usb_serial_port *port,
 	struct iuu_private *priv = usb_get_serial_port_data(port);
 	unsigned long flags;
 
-	if (count > 256)
-		return -ENOMEM;
-
 	spin_lock_irqsave(&priv->lock, flags);
 
+	count = min(count, 256 - priv->writelen);
+	if (count == 0)
+		goto out;
+
 	/* fill the buffer */
 	memcpy(priv->writebuf + priv->writelen, buf, count);
 	priv->writelen += count;
+out:
 	spin_unlock_irqrestore(&priv->lock, flags);
 
 	return count;