tty: serial: max3100: Fix error case

We don't want to free a random address if the entry is wrong, cover
this and WARN if it ever happens.

Signed-off-by: Alan Cox <alan@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/max3100.c

@@ -827,14 +827,16 @@ static int __devexit max3100_remove(struct spi_device *spi)
 
 	/* find out the index for the chip we are removing */
 	for (i = 0; i < MAX_MAX3100; i++)
-		if (max3100s[i] == s)
+		if (max3100s[i] == s) {
+			dev_dbg(&spi->dev, "%s: removing port %d\n", __func__, i);
+			uart_remove_one_port(&max3100_uart_driver, &max3100s[i]->port);
+			kfree(max3100s[i]);
+			max3100s[i] = NULL;
 			break;
+		}
 
-	dev_dbg(&spi->dev, "%s: removing port %d\n", __func__, i);
-	uart_remove_one_port(&max3100_uart_driver, &max3100s[i]->port);
-	kfree(max3100s[i]);
-	max3100s[i] = NULL;
-
+	WARN_ON(i == MAX_MAX3100);
+
 	/* check if this is the last chip we have */
 	for (i = 0; i < MAX_MAX3100; i++)
 		if (max3100s[i]) {