linux-kernel - [PATCH 2/8] gpiolib: sanitize the return value of gpio

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Message-Id: <20250210-gpio-sanitize-retvals-v1-2-12ea88506cb2@linaro.org>
Date: Mon, 10 Feb 2025 11:51:56 +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 2/8] gpiolib: sanitize the return value of
 gpio_chip::request()

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

The return value of the request() callback may be propagated to
user-space. If a bad driver returns a positive number, it may confuse
user programs. Tighten the API contract and check for positive numbers
returned by GPIO controllers.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
---
 drivers/gpio/gpiolib.c      | 2 ++
 include/linux/gpio/driver.h | 3 ++-
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 5d3774dc748b..42625da7e797 100644
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2331,6 +2331,8 @@ static int gpiod_request_commit(struct gpio_desc *desc, const char *label)
 			ret = guard.gc->request(guard.gc, offset);
 		else
 			ret = -EINVAL;
+		if (ret > 0)
+			ret = -EBADE;
 		if (ret)
 			goto out_clear_bit;
 	}
diff --git a/include/linux/gpio/driver.h b/include/linux/gpio/driver.h
index 2dd7cb9cc270..26fcddcb74b8 100644
--- a/include/linux/gpio/driver.h
+++ b/include/linux/gpio/driver.h
@@ -328,7 +328,8 @@ struct gpio_irq_chip {
  * @fwnode: optional fwnode providing this controller's properties
  * @owner: helps prevent removal of modules exporting active GPIOs
  * @request: optional hook for chip-specific activation, such as
- *	enabling module power and clock; may sleep
+ *	enabling module power and clock; may sleep; must return 0 on success
+ *	or negative error number on failure
  * @free: optional hook for chip-specific deactivation, such as
  *	disabling module power and clock; may sleep
  * @get_direction: returns direction for signal "offset", 0=out, 1=in,

-- 
2.45.2