linux-kernel - [PATCH 4.15 025/168] gpiolib: dont dereference a desc before validation

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Message-Id: <20180410212801.267806966@linuxfoundation.org>
Date:   Wed, 11 Apr 2018 00:22:47 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Vladimir Zapolskiy <vz@...ia.com>,
        Linus Walleij <linus.walleij@...aro.org>,
        Sasha Levin <alexander.levin@...rosoft.com>
Subject: [PATCH 4.15 025/168] gpiolib: dont dereference a desc before validation

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

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

From: Vladimir Zapolskiy <vz@...ia.com>


[ Upstream commit 30322bcf82d74cad0d6e1cf9ba7fa7fa48c7a026 ]

The fix restores a proper validation of an input gpio desc, which
might be needed to deal with optional GPIOs correctly.

Fixes: 02e479808b5d ("gpio: Alter semantics of *raw* operations to actually be raw")
Signed-off-by: Vladimir Zapolskiy <vz@...ia.com>
Signed-off-by: Linus Walleij <linus.walleij@...aro.org>
Signed-off-by: Sasha Levin <alexander.levin@...rosoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/gpio/gpiolib.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2468,7 +2468,7 @@ EXPORT_SYMBOL_GPL(gpiod_direction_output
  */
 int gpiod_direction_output(struct gpio_desc *desc, int value)
 {
-	struct gpio_chip *gc = desc->gdev->chip;
+	struct gpio_chip *gc;
 	int ret;
 
 	VALIDATE_DESC(desc);
@@ -2485,6 +2485,7 @@ int gpiod_direction_output(struct gpio_d
 		return -EIO;
 	}
 
+	gc = desc->gdev->chip;
 	if (test_bit(FLAG_OPEN_DRAIN, &desc->flags)) {
 		/* First see if we can enable open drain in hardware */
 		ret = gpio_set_drive_single_ended(gc, gpio_chip_hwgpio(desc),