linux-kernel - [PATCH v2 6/9] serial: samsung: Fix out-of-bounds access through serial port index

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Date:   Fri, 23 Feb 2018 14:38:34 +0100
From:   Geert Uytterhoeven <geert+renesas@...der.be>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Barry Song <baohua@...nel.org>, Vineet Gupta <vgupta@...opsys.com>,
        Jiri Slaby <jslaby@...e.com>,
        Michal Simek <michal.simek@...inx.com>,
        linux-serial@...r.kernel.org, linux-snps-arc@...ts.infradead.org,
        linux-renesas-soc@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Geert Uytterhoeven <geert+renesas@...der.be>
Subject: [PATCH v2 6/9] serial: samsung: Fix out-of-bounds access through serial port index

The s3c24xx_serial_ports[] array is indexed using a value derived from
the "serialN" alias in DT, or from an incrementing probe index, 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_SAMSUNG_UARTS), so this can even be triggered using
a legitimate DTB or legitimate board code.

Fixes: 13a9f6c64fdc55eb ("serial: samsung: Consider DT alias when probing ports")
Signed-off-by: Geert Uytterhoeven <geert+renesas@...der.be>
---
v2:
  - Fix Fixes reference,
  - Use ARRAY_SIZE(),
  - Update patch description for non-DT case.
---
 drivers/tty/serial/samsung.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/drivers/tty/serial/samsung.c b/drivers/tty/serial/samsung.c
index f9fecc5ed0cee826..3f2f8c118ce09d56 100644
--- a/drivers/tty/serial/samsung.c
+++ b/drivers/tty/serial/samsung.c
@@ -1818,6 +1818,10 @@ static int s3c24xx_serial_probe(struct platform_device *pdev)
 
 	dbg("s3c24xx_serial_probe(%p) %d\n", pdev, index);
 
+	if (index >= ARRAY_SIZE(s3c24xx_serial_ports)) {
+		dev_err(&pdev->dev, "serial%d out of range\n", index);
+		return -EINVAL;
+	}
 	ourport = &s3c24xx_serial_ports[index];
 
 	ourport->drv_data = s3c24xx_get_driver_data(pdev);
-- 
2.7.4