linux-kernel - [PATCH 6/8] gpiolib: sanitize the return value of gpio_chip::direction

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Message-Id: <20250210-gpio-sanitize-retvals-v1-6-12ea88506cb2@linaro.org>
Date: Mon, 10 Feb 2025 11:52:00 +0100
From: Bartosz Golaszewski <brgl@...ev.pl>
To: Linus Walleij <linus.walleij@...aro.org>, 
 Bartosz Golaszewski <brgl@...ev.pl>
Cc: linux-gpio@...r.kernel.org, linux-kernel@...r.kernel.org, 
 Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Subject: [PATCH 6/8] gpiolib: sanitize the return value of
 gpio_chip::direction_output()

From: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>

The return value of the direction_output() callback may be propagated to
user-space. As per the API contract it can only return 0 or a negative
error number. Add a wrapper around the callback calls that filters out
anything else.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/gpio/gpiolib.c | 25 +++++++++++++++++++++----
 1 file changed, 21 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 7255f4df6a8b..1f75ae6e208c 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2683,6 +2683,23 @@ int gpio_set_debounce_timeout(struct gpio_desc *desc, unsigned int debounce)
 	return ret;
 }
 
+static int gpiochip_direction_output(struct gpio_chip *gc, unsigned int offset,
+				     int value)
+{
+	int ret;
+
+	lockdep_assert_held(&gc->gpiodev->srcu);
+
+	if (WARN_ON(!gc->direction_output))
+		return -EOPNOTSUPP;
+
+	ret = gc->direction_output(gc, offset, value);
+	if (ret > 0)
+		ret = -EBADE;
+
+	return ret;
+}
+
 /**
  * gpiod_direction_input - set the GPIO direction to input
  * @desc:	GPIO to set to input
@@ -2780,8 +2797,8 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
 	}
 
 	if (guard.gc->direction_output) {
-		ret = guard.gc->direction_output(guard.gc,
-						 gpio_chip_hwgpio(desc), val);
+		ret = gpiochip_direction_output(guard.gc,
+						gpio_chip_hwgpio(desc), val);
 	} else {
 		/* Check that we are in output mode if we can */
 		if (guard.gc->get_direction) {
@@ -3433,7 +3450,7 @@ static void gpio_set_open_drain_value_commit(struct gpio_desc *desc, bool value)
 	if (value) {
 		ret = guard.gc->direction_input(guard.gc, offset);
 	} else {
-		ret = guard.gc->direction_output(guard.gc, offset, 0);
+		ret = gpiochip_direction_output(guard.gc, offset, 0);
 		if (!ret)
 			set_bit(FLAG_IS_OUT, &desc->flags);
 	}
@@ -3458,7 +3475,7 @@ static void gpio_set_open_source_value_commit(struct gpio_desc *desc, bool value
 		return;
 
 	if (value) {
-		ret = guard.gc->direction_output(guard.gc, offset, 1);
+		ret = gpiochip_direction_output(guard.gc, offset, 1);
 		if (!ret)
 			set_bit(FLAG_IS_OUT, &desc->flags);
 	} else {

-- 
2.45.2