USB: serial: ark3116: fix open error handling

commit b631433b upstream.

Fix open error handling which failed to detect errors when reading the
MSR and LSR registers, something which could lead to the shadow
registers being initialised from errnos.

Note that calling the generic close implementation is sufficient in the
error paths as the interrupt urb has not yet been submitted and the
register updates have not been made.

Fixes: f4c1e8d5 ("USB: ark3116: Make existing functions 16450-aware
and add close and release functions.")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/serial/ark3116.c

@@ -382,23 +382,29 @@ static int ark3116_open(struct tty_struct *tty, struct usb_serial_port *port)
 	if (result) {
 		dbg("%s - usb_serial_generic_open failed: %d",
 		    __func__, result);
-		goto err_out;
+		goto err_free;
 	}
 
 	/* remove any data still left: also clears error state */
 	ark3116_read_reg(serial, UART_RX, buf);
 
 	/* read modem status */
-	priv->msr = ark3116_read_reg(serial, UART_MSR, buf);
+	result = ark3116_read_reg(serial, UART_MSR, buf);
+	if (result < 0)
+		goto err_close;
+	priv->msr = *buf;
+
 	/* read line status */
-	priv->lsr = ark3116_read_reg(serial, UART_LSR, buf);
+	result = ark3116_read_reg(serial, UART_LSR, buf);
+	if (result < 0)
+		goto err_close;
+	priv->lsr = *buf;
 
 	result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
 	if (result) {
 		dev_err(&port->dev, "submit irq_in urb failed %d\n",
 			result);
-		ark3116_close(port);
-		goto err_out;
+		goto err_close;
 	}
 
 	/* activate interrupts */
@@ -411,8 +417,15 @@ static int ark3116_open(struct tty_struct *tty, struct usb_serial_port *port)
 	if (tty)
 		ark3116_set_termios(tty, port, NULL);
 
-err_out:
 	kfree(buf);
+
+	return 0;
+
+err_close:
+	usb_serial_generic_close(port);
+err_free:
+	kfree(buf);
+
 	return result;
 }