[PATCH 4.14 151/165] serial: sh-sci: Fix out-of-bounds access through DT alias

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Geert Uytterhoeven <geert+rene...@glider.be>

[ Upstream commit 090fa4b0dccfa3d04e1c5ab0fe4eba16e6713895 ]

The sci_ports[] array is indexed using a value derived from the
"serialN" alias in DT, which may lead to an out-of-bounds access.

Fix this by adding a range check.

Note that the array size is defined by a Kconfig symbol
(CONFIG_SERIAL_SH_SCI_NR_UARTS), so this can even be triggered using a
legitimate DTB.

Fixes: 97ed9790c514066b ("serial: sh-sci: Remove unused platform data 
capabilities field")
Signed-off-by: Geert Uytterhoeven <geert+rene...@glider.be>
Signed-off-by: Sasha Levin <alexander.le...@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>
---
 drivers/tty/serial/sh-sci.c |    4 ++++
 1 file changed, 4 insertions(+)

--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -3076,6 +3076,10 @@ static struct plat_sci_port *sci_parse_d
                dev_err(&pdev->dev, "failed to get alias id (%d)\n", id);
                return NULL;
        }
+       if (id >= ARRAY_SIZE(sci_ports)) {
+               dev_err(&pdev->dev, "serial%d out of range\n", id);
+               return NULL;
+       }
 
        sp = &sci_ports[id];
        *dev_id = id;