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Commit 72eba6f6 authored by Johan Hovold's avatar Johan Hovold Committed by Linus Walleij
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gpio: sysfs: fix race between gpiod export and unexport 



Make sure to deregister the class device (and release the irq) while
holding the sysfs lock in gpio_unexport to prevent racing with
gpio_export.

Note that this requires the recently introduced per-gpio locking to
avoid a deadlock with the kernfs active protection when waiting for the
attribute operations to drain during deregistration.

Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
Reviewed-by: default avatarAlexandre Courbot <acourbot@nvidia.com>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 6ffcb797

drivers/gpio/gpiolib-sysfs.c

+26 −25
Original line number Diff line number Diff line
@@ -675,8 +675,7 @@ EXPORT_SYMBOL_GPL(gpiod_export_link); 
void gpiod_unexport(struct gpio_desc *desc)

{

	struct gpiod_data *data;

	int			status = 0;

	struct device		*dev = NULL;

	struct device *dev;



	if (!desc) {

		pr_warn("%s: invalid GPIO\n", __func__);
@@ -685,33 +684,35 @@ void gpiod_unexport(struct gpio_desc *desc) 


	mutex_lock(&sysfs_lock);



	if (test_bit(FLAG_EXPORT, &desc->flags)) {

	if (!test_bit(FLAG_EXPORT, &desc->flags))

		goto err_unlock;



	dev = class_find_device(&gpio_class, NULL, desc, match_export);

		if (dev) {

	if (!dev)

		goto err_unlock;



	data = dev_get_drvdata(dev);



	clear_bit(FLAG_SYSFS_DIR, &desc->flags);

	clear_bit(FLAG_EXPORT, &desc->flags);

		} else

			status = -ENODEV;

	}



	mutex_unlock(&sysfs_lock);



	if (dev) {

		data = dev_get_drvdata(dev);

	device_unregister(dev);



	/*

		 * Release irq after deregistration to prevent race with

		 * edge_store.

	 * Release irq after deregistration to prevent race with edge_store.

	 */

	if (desc->flags & GPIO_TRIGGER_MASK)

		gpio_sysfs_free_irq(dev);



	mutex_unlock(&sysfs_lock);



	put_device(dev);

	kfree(data);

	}



	if (status)

		gpiod_dbg(desc, "%s: status %d\n", __func__, status);

	return;



err_unlock:

	mutex_unlock(&sysfs_lock);

}

EXPORT_SYMBOL_GPL(gpiod_unexport);