gpiolib: fix a NULL-pointer dereference when setting direction

For optional GPIOs we may pass NULL to gpiod_direction_(input|output)().
With the call to the notifier chain added by commit 07c61d4da43f
("gpiolib: notify user-space about in-kernel line state changes") we
will now dereference a NULL pointer in this case. The reason for that is
the fact that the expansion of the VALIDATE_DESC() macro (which returns
0 for NULL descriptors) was moved into the nonotify variants of the
direction setters.

Move them back to the top-level interfaces as the nonotify ones are only
ever called from inside the GPIO core and are always passed valid GPIO
descriptors. This way we'll never call the line_state notifier chain
with non-valid descs.

Fixes: 07c61d4da43f ("gpiolib: notify user-space about in-kernel line state changes")
Reported-by: Mark Brown <broonie@kernel.org>
Closes: https://lore.kernel.org/all/d6601a31-7685-4b21-9271-1b76116cc483@sirena.org.uk/
Tested-by: Klara Modin <klarasmodin@gmail.com>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/r/20241024133834.47395-1-brgl@bgdev.pl
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index ae758ba6dc3d1a058a5983d4ff66535b46ad94c0..6001ec96693c5f84e34f89584533b5d2af0bd9a5 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2695,6 +2695,8 @@ int gpiod_direction_input(struct gpio_desc *desc)
 {
        int ret;
 
+       VALIDATE_DESC(desc);
+
        ret = gpiod_direction_input_nonotify(desc);
        if (ret == 0)
                gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
@@ -2707,8 +2709,6 @@ int gpiod_direction_input_nonotify(struct gpio_desc *desc)
 {
        int ret = 0;
 
-       VALIDATE_DESC(desc);
-
        CLASS(gpio_chip_guard, guard)(desc);
        if (!guard.gc)
                return -ENODEV;
@@ -2841,6 +2841,8 @@ int gpiod_direction_output(struct gpio_desc *desc, int value)
 {
        int ret;
 
+       VALIDATE_DESC(desc);
+
        ret = gpiod_direction_output_nonotify(desc, value);
        if (ret == 0)
                gpiod_line_state_notify(desc, GPIO_V2_LINE_CHANGED_CONFIG);
@@ -2854,8 +2856,6 @@ int gpiod_direction_output_nonotify(struct gpio_desc *desc, int value)
        unsigned long flags;
        int ret;
 
-       VALIDATE_DESC(desc);
-
        flags = READ_ONCE(desc->flags);
 
        if (test_bit(FLAG_ACTIVE_LOW, &flags))