serial: sh-sci: Fix out-of-bounds access through DT alias

BugLink: http://bugs.launchpad.net/bugs/1783418
[ 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+renesas@glider.be>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c
index 44adf9db38f8955b6cf730108abe5d72c87ef3e9..ab757546c6db8bcbc44391a6b194ea2143d33351 100644 (file)
--- a/drivers/tty/serial/sh-sci.c
+++ b/drivers/tty/serial/sh-sci.c
@@ -3098,6 +3098,10 @@ static struct plat_sci_port *sci_parse_dt(struct platform_device *pdev,
                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;