gpiolib: sanitize the return value of gpio_chip::direction_output()

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.

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Link: https://lore.kernel.org/r/20250210-gpio-sanitize-retvals-v1-6-12ea88506cb2@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 9ac2dad0ad3429d0f6c3a1e61abdd4699f8749ca..2c8c4183f6f0b5db2ffd7a7a438ac75079ecc896 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2701,6 +2701,23 @@ 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
@@ -2798,8 +2815,8 @@ 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) {
@@ -3460,7 +3477,7 @@ 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);
        }
@@ -3485,7 +3502,7 @@ 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 {