linux-kernel - [PATCH 7/8] gpiolib: sanitize the return value of gpio_chip::direction

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Message-Id: <20250210-gpio-sanitize-retvals-v1-7-12ea88506cb2@linaro.org>
Date: Mon, 10 Feb 2025 11:52:01 +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 7/8] gpiolib: sanitize the return value of
 gpio_chip::direction_input()

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

The return value of the direction_input() 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 | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 1f75ae6e208c..683a03d237c0 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2683,6 +2683,22 @@ int gpio_set_debounce_timeout(struct gpio_desc *desc, unsigned int debounce)
 	return ret;
 }
 
+static int gpiochip_direction_input(struct gpio_chip *gc, unsigned int offset)
+{
+	int ret;
+
+	lockdep_assert_held(&gc->gpiodev->srcu);
+
+	if (WARN_ON(!gc->direction_input))
+		return -EOPNOTSUPP;
+
+	ret = gc->direction_input(gc, offset);
+	if (ret > 0)
+		ret = -EBADE;
+
+	return ret;
+}
+
 static int gpiochip_direction_output(struct gpio_chip *gc, unsigned int offset,
 				     int value)
 {
@@ -2751,8 +2767,8 @@ int gpiod_direction_input_nonotify(struct gpio_desc *desc)
 	 * assume we are in input mode after this.
 	 */
 	if (guard.gc->direction_input) {
-		ret = guard.gc->direction_input(guard.gc,
-						gpio_chip_hwgpio(desc));
+		ret = gpiochip_direction_input(guard.gc,
+					       gpio_chip_hwgpio(desc));
 	} else if (guard.gc->get_direction) {
 		ret = guard.gc->get_direction(guard.gc,
 					      gpio_chip_hwgpio(desc));
@@ -3448,7 +3464,7 @@ static void gpio_set_open_drain_value_commit(struct gpio_desc *desc, bool value)
 		return;
 
 	if (value) {
-		ret = guard.gc->direction_input(guard.gc, offset);
+		ret = gpiochip_direction_input(guard.gc, offset);
 	} else {
 		ret = gpiochip_direction_output(guard.gc, offset, 0);
 		if (!ret)
@@ -3479,7 +3495,7 @@ static void gpio_set_open_source_value_commit(struct gpio_desc *desc, bool value
 		if (!ret)
 			set_bit(FLAG_IS_OUT, &desc->flags);
 	} else {
-		ret = guard.gc->direction_input(guard.gc, offset);
+		ret = gpiochip_direction_input(guard.gc, offset);
 	}
 	trace_gpio_direction(desc_to_gpio(desc), !value, ret);
 	if (ret < 0)

-- 
2.45.2