linux-kernel - [PATCH V2 1/2] serial: mctrl_gpio: Check for NULL pointer

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Date:   Sun,  6 Oct 2019 11:33:11 -0500
From:   Adam Ford <aford173@...il.com>
To:     linux-serial@...r.kernel.org
Cc:     Adam Ford <aford173@...il.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jiri Slaby <jslaby@...e.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Vignesh R <vigneshr@...com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Douglas Anderson <dianders@...omium.org>,
        Tony Lindgren <tony@...mide.com>,
        Yegor Yefremov <yegorslists@...glemail.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH V2 1/2] serial: mctrl_gpio: Check for NULL pointer

When using mctrl_gpio_to_gpiod, it dereferences gpios into a single
requested GPIO.  This dereferencing can break if gpios is NULL,
so this patch adds a NULL check before dereferencing it.  If
gpios is NULL, this function will also return NULL.

Signed-off-by: Adam Ford <aford173@...il.com>
---
V2:  This patch is new to the V2 of this series, so patch 2/2 can 
     work without risking a NULL dereference
diff --git a/drivers/tty/serial/serial_mctrl_gpio.c b/drivers/tty/serial/serial_mctrl_gpio.c
index d9074303c88e..fb4781292d40 100644
--- a/drivers/tty/serial/serial_mctrl_gpio.c
+++ b/drivers/tty/serial/serial_mctrl_gpio.c
@@ -66,6 +66,9 @@ 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