linux-kernel - [PATCH v3 2/4] serial: mctrl_gpio: Add a NULL check to mctrl_gpio_to

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Message-ID: <20190802100349.8659-2-frieder.schrempf@kontron.de>
Date:   Fri, 2 Aug 2019 10:04:10 +0000
From:   Schrempf Frieder <frieder.schrempf@...tron.de>
To:     "u.kleine-koenig@...gutronix.de" <u.kleine-koenig@...gutronix.de>,
        "shawnguo@...nel.org" <shawnguo@...nel.org>,
        "s.hauer@...gutronix.de" <s.hauer@...gutronix.de>,
        "kernel@...gutronix.de" <kernel@...gutronix.de>,
        "festevam@...il.com" <festevam@...il.com>,
        "linux-imx@....com" <linux-imx@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "geert+renesas@...der.be" <geert+renesas@...der.be>,
        Schrempf Frieder <frieder.schrempf@...tron.de>,
        Jiri Slaby <jslaby@...e.com>,
        "linux-serial@...r.kernel.org" <linux-serial@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: [PATCH v3 2/4] serial: mctrl_gpio: Add a NULL check to
 mctrl_gpio_to_gpiod()

From: Frieder Schrempf <frieder.schrempf@...tron.de>

As it is allowed to use the mctrl_gpio_* functions before
initialization (as the 8250 driver does according to 434be0ae7aa7),
it seems appropriate to have a NULL check in all of the functions.
Otherwise the mctrl_gpio_to_gpiod() function is prone to be used
in a context that can lead to a NULL pointer dereference.

Signed-off-by: Frieder Schrempf <frieder.schrempf@...tron.de>
---
Changes in v3
=============
* Move the changes in mctrl_gpio_to_gpiod() to a separate patch
---
 drivers/tty/serial/serial_mctrl_gpio.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
index 2b400189be91..54c43e02e375 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.c
+++ b/drivers/tty/serial/serial_mctrl_gpio.c
@@ -61,6 +61,9 @@ EXPORT_SYMBOL_GPL(mctrl_gpio_set);
 struct gpio_desc *mctrl_gpio_to_gpiod(struct mctrl_gpios *gpios,
 				      enum mctrl_gpio_idx gidx)
 {
+	if (gpios == NULL)
+		return NULL;
+
 	return gpios->gpio[gidx];
 }
 EXPORT_SYMBOL_GPL(mctrl_gpio_to_gpiod);
-- 
2.17.1