diff --git a/drivers/tty/serial/8250/8250_of.c b/drivers/tty/serial/8250/8250_of.c
index 8fedc075fb1e..a76533a48245 100644
--- a/drivers/tty/serial/8250/8250_of.c
+++ b/drivers/tty/serial/8250/8250_of.c
@@ -104,8 +104,17 @@ static int of_platform_serial_setup(struct platform_device *ofdev,
 		port->mapsize = resource_size(&resource);
 
 		/* Check for shifted address mapping */
-		if (of_property_read_u32(np, "reg-offset", &prop) == 0)
+		if (of_property_read_u32(np, "reg-offset", &prop) == 0) {
+			if (prop >= port->mapsize) {
+				dev_warn(&ofdev->dev, "reg-offset %u exceeds region size %pa\n",
+					 prop, &port->mapsize);
+				ret = -EINVAL;
+				goto err_unprepare;
+			}
+
 			port->mapbase += prop;
+			port->mapsize -= prop;
+		}
 
 		port->iotype = UPIO_MEM;
 		if (of_property_read_u32(np, "reg-io-width", &prop) == 0) {