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Commit ebbeba12 authored by Johan Hovold's avatar Johan Hovold Committed by Linus Walleij
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gpio: sysfs: fix gpio attribute-creation race 



Fix attribute-creation race with userspace by using the default group
to create also the contingent gpio device attributes.

Fixes: d8f388d8 ("gpio: sysfs interface")
Signed-off-by: default avatarJohan Hovold <johan@kernel.org>
Signed-off-by: default avatarLinus Walleij <linus.walleij@linaro.org>
parent 0915e6fe

drivers/gpio/gpiolib-sysfs.c

+39 −22
Original line number Diff line number Diff line
@@ -356,12 +356,44 @@ static ssize_t gpio_active_low_store(struct device *dev, 
static DEVICE_ATTR(active_low, 0644,

		gpio_active_low_show, gpio_active_low_store);



static umode_t gpio_is_visible(struct kobject *kobj, struct attribute *attr,

			       int n)

{

	struct device *dev = container_of(kobj, struct device, kobj);

	struct gpio_desc *desc = dev_get_drvdata(dev);

	umode_t mode = attr->mode;

	bool show_direction = test_bit(FLAG_SYSFS_DIR, &desc->flags);



	if (attr == &dev_attr_direction.attr) {

		if (!show_direction)

			mode = 0;

	} else if (attr == &dev_attr_edge.attr) {

		if (gpiod_to_irq(desc) < 0)

			mode = 0;

		if (!show_direction && test_bit(FLAG_IS_OUT, &desc->flags))

			mode = 0;

	}



	return mode;

}



static struct attribute *gpio_attrs[] = {

	&dev_attr_direction.attr,

	&dev_attr_edge.attr,

	&dev_attr_value.attr,

	&dev_attr_active_low.attr,

	NULL,

};

ATTRIBUTE_GROUPS(gpio);



static const struct attribute_group gpio_group = {

	.attrs = gpio_attrs,

	.is_visible = gpio_is_visible,

};



static const struct attribute_group *gpio_groups[] = {

	&gpio_group,

	NULL

};



/*

 * /sys/class/gpio/gpiochipN/
@@ -550,8 +582,11 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change) 
		goto fail_unlock;

	}



	if (!desc->chip->direction_input || !desc->chip->direction_output)

		direction_may_change = false;

	if (desc->chip->direction_input && desc->chip->direction_output &&

			direction_may_change) {

		set_bit(FLAG_SYSFS_DIR, &desc->flags);

	}



	spin_unlock_irqrestore(&gpio_lock, flags);



	offset = gpio_chip_hwgpio(desc);
@@ -567,27 +602,10 @@ int gpiod_export(struct gpio_desc *desc, bool direction_may_change) 
		goto fail_unlock;

	}



	if (direction_may_change) {

		status = device_create_file(dev, &dev_attr_direction);

		if (status)

			goto fail_unregister_device;

	}



	if (gpiod_to_irq(desc) >= 0 && (direction_may_change ||

				       !test_bit(FLAG_IS_OUT, &desc->flags))) {

		status = device_create_file(dev, &dev_attr_edge);

		if (status)

			goto fail_remove_attr_direction;

	}



	set_bit(FLAG_EXPORT, &desc->flags);

	mutex_unlock(&sysfs_lock);

	return 0;



fail_remove_attr_direction:

	device_remove_file(dev, &dev_attr_direction);

fail_unregister_device:

	device_unregister(dev);

fail_unlock:

	mutex_unlock(&sysfs_lock);

	gpiod_dbg(desc, "%s: status %d\n", __func__, status);
@@ -711,6 +729,7 @@ void gpiod_unexport(struct gpio_desc *desc) 
		dev = class_find_device(&gpio_class, NULL, desc, match_export);

		if (dev) {

			gpio_setup_irq(desc, dev, 0);

			clear_bit(FLAG_SYSFS_DIR, &desc->flags);

			clear_bit(FLAG_EXPORT, &desc->flags);

		} else

			status = -ENODEV;
@@ -719,8 +738,6 @@ void gpiod_unexport(struct gpio_desc *desc) 
	mutex_unlock(&sysfs_lock);



	if (dev) {

		device_remove_file(dev, &dev_attr_edge);

		device_remove_file(dev, &dev_attr_direction);

		device_unregister(dev);

		put_device(dev);

	}

drivers/gpio/gpiolib.h

+1 −0
Original line number Diff line number Diff line
@@ -77,6 +77,7 @@ struct gpio_desc { 
#define FLAG_OPEN_DRAIN	7	/* Gpio is open drain type */

#define FLAG_OPEN_SOURCE 8	/* Gpio is open source type */

#define FLAG_USED_AS_IRQ 9	/* GPIO is connected to an IRQ */

#define FLAG_SYSFS_DIR	10	/* show sysfs direction attribute */



#define ID_SHIFT	16	/* add new flags before this one */