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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: d8f388d8dc ("gpio: sysfs interface")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
This commit is contained in:
Johan Hovold 2015-01-13 13:00:06 +01:00 committed by Linus Walleij
parent 0915e6feb3
commit ebbeba120a
2 changed files with 40 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

61
drivers/gpio/gpiolib-sysfs.c
View File

@ -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);
}

1
drivers/gpio/gpiolib.h
View File

@ -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 */