gpiolib: Fix unaligned used of reference counters

gpiolib relies on the reference counters to clean up the gpio_device
structure.

Although the number of get/put is properly aligned on gpiolib.c
itself, it does not take into consideration how the referece counters
are affected by other external functions such as cdev_add and device_add.

Because of this, after the last call to put_device, the reference counter
has a value of +3, therefore never calling gpiodevice_release.

Due to the fact that some of the device  has already been cleaned on
gpiochip_remove, the library will end up OOPsing the kernel (e.g. a call
to of_gpiochip_find_and_xlate).

Cc: stable@vger.kernel.org
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

diff --git a/drivers/gpio/gpiolib.c b/drivers/gpio/gpiolib.c
index a2c31a5..58d822d 100644 (file)
--- a/drivers/gpio/gpiolib.c
+++ b/drivers/gpio/gpiolib.c
@@ -449,7 +449,6 @@ static void gpiodevice_release(struct device *dev)
 {
        struct gpio_device *gdev = dev_get_drvdata(dev);
 
-       cdev_del(&gdev->chrdev);
        list_del(&gdev->list);
        ida_simple_remove(&gpio_ida, gdev->id);
        kfree(gdev->label);
@@ -482,7 +481,6 @@ static int gpiochip_setup_dev(struct gpio_device *gdev)
 
        /* From this point, the .release() function cleans up gpio_device */
        gdev->dev.release = gpiodevice_release;
-       get_device(&gdev->dev);
        pr_debug("%s: registered GPIOs %d to %d on device: %s (%s)\n",
                 __func__, gdev->base, gdev->base + gdev->ngpio - 1,
                 dev_name(&gdev->dev), gdev->chip->label ? : "generic");
@@ -770,6 +768,8 @@ void gpiochip_remove(struct gpio_chip *chip)
         * be removed, else it will be dangling until the last user is
         * gone.
         */
+       cdev_del(&gdev->chrdev);
+       device_del(&gdev->dev);
        put_device(&gdev->dev);
 }
 EXPORT_SYMBOL_GPL(gpiochip_remove);