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

As per the API contract, the get_direction() callback can only
return 0, 1 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-v1-8-12ea88506cb2@linaro.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index e720a1d2f343bd75bb539378385103390f71cfd7..9103384f4a5e7341e0fc963a5fcc648405a04055 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -342,6 +342,22 @@ static int gpiochip_find_base_unlocked(u16 ngpio)
        }
 }
 
+static int gpiochip_get_direction(struct gpio_chip *gc, unsigned int offset)
+{
+       int ret;
+
+       lockdep_assert_held(&gc->gpiodev->srcu);
+
+       if (WARN_ON(!gc->get_direction))
+               return -EOPNOTSUPP;
+
+       ret = gc->get_direction(gc, offset);
+       if (ret > 1)
+               ret = -EBADE;
+
+       return ret;
+}
+
 /**
  * gpiod_get_direction - return the current direction of a GPIO
  * @desc:      GPIO to get the direction of
@@ -382,7 +398,7 @@ int gpiod_get_direction(struct gpio_desc *desc)
        if (!guard.gc->get_direction)
                return -ENOTSUPP;
 
-       ret = guard.gc->get_direction(guard.gc, offset);
+       ret = gpiochip_get_direction(guard.gc, offset);
        if (ret < 0)
                return ret;
 
@@ -1067,7 +1083,7 @@ int gpiochip_add_data_with_key(struct gpio_chip *gc, void *data,
                desc->gdev = gdev;
 
                if (gc->get_direction && gpiochip_line_is_valid(gc, desc_index)) {
-                       ret = gc->get_direction(gc, desc_index);
+                       ret = gpiochip_get_direction(gc, desc_index);
                        if (ret < 0)
                                /*
                                 * FIXME: Bail-out here once all GPIO drivers
@@ -2788,8 +2804,7 @@ int gpiod_direction_input_nonotify(struct gpio_desc *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));
+               ret = gpiochip_get_direction(guard.gc, gpio_chip_hwgpio(desc));
                if (ret < 0)
                        return ret;
 
@@ -2836,8 +2851,8 @@ static int gpiod_direction_output_raw_commit(struct gpio_desc *desc, int value)
        } else {
                /* Check that we are in output mode if we can */
                if (guard.gc->get_direction) {
-                       ret = guard.gc->get_direction(guard.gc,
-                                                     gpio_chip_hwgpio(desc));
+                       ret = gpiochip_get_direction(guard.gc,
+                                                    gpio_chip_hwgpio(desc));
                        if (ret < 0)
                                return ret;