gpiolib: fix reference leaks when removing GPIO chips still in use

After we remove a GPIO chip that still has some requested descriptors,
gpiod_free_commit() will fail and we will never put the references to the
GPIO device and the owning module in gpiod_free().

Rework this function to:
- not warn on desc == NULL as this is a use-case on which most free
  functions silently return
- put the references to desc->gdev and desc->gdev->owner unconditionally
  so that the release callback actually gets called when the remaining
  references are dropped by external GPIO users

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index 251c875b5c34cc563e113cf1f4ec257b31a2c213..76e0c38026c3e94b87566a35eb98b6bc40fb2061 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -2167,12 +2167,18 @@ static bool gpiod_free_commit(struct gpio_desc *desc)
 
 void gpiod_free(struct gpio_desc *desc)
 {
-       if (desc && desc->gdev && gpiod_free_commit(desc)) {
-               module_put(desc->gdev->owner);
-               gpio_device_put(desc->gdev);
-       } else {
+       /*
+        * We must not use VALIDATE_DESC_VOID() as the underlying gdev->chip
+        * may already be NULL but we still want to put the references.
+        */
+       if (!desc)
+               return;
+
+       if (!gpiod_free_commit(desc))
                WARN_ON(extra_checks);
-       }
+
+       module_put(desc->gdev->owner);
+       gpio_device_put(desc->gdev);
 }
 
 /**