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: d8f388d8dc8d ("gpio: sysfs interface")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
diff --git a/drivers/gpio/gpiolib-sysfs.c b/drivers/gpio/gpiolib-sysfs.c
index fd4d942..f62aa11 100644
--- a/drivers/gpio/gpiolib-sysfs.c
+++ b/drivers/gpio/gpiolib-sysfs.c
@@ -356,12 +356,44 @@
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 @@
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 @@
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 @@
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 @@
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);
}