ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

1 files changed, 514 insertions, 0 deletions

diff --git a/drivers/leds/led-triggers.c b/drivers/leds/led-triggers.c
new file mode 100644
index 000000000..b1223218b
--- /dev/null
+++ b/drivers/leds/led-triggers.c
@@ -0,0 +1,514 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * LED Triggers Core
+ *
+ * Copyright 2005-2007 Openedhand Ltd.
+ *
+ * Author: Richard Purdie <rpurdie@openedhand.com>
+ */
+
+#include <linux/export.h>
+#include <linux/kernel.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/device.h>
+#include <linux/timer.h>
+#include <linux/rwsem.h>
+#include <linux/leds.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+#include "leds.h"
+
+/*
+ * Nests outside led_cdev->trigger_lock
+ */
+static DECLARE_RWSEM(triggers_list_lock);
+static LIST_HEAD(trigger_list);
+
+ /* Used by LED Class */
+
+static inline bool
+trigger_relevant(struct led_classdev *led_cdev, struct led_trigger *trig)
+{
+	return !trig->trigger_type || trig->trigger_type == led_cdev->trigger_type;
+}
+
+ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
+			  const struct bin_attribute *bin_attr, char *buf,
+			  loff_t pos, size_t count)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	struct led_trigger *trig;
+	int ret = count;
+
+	mutex_lock(&led_cdev->led_access);
+
+	if (led_sysfs_is_disabled(led_cdev)) {
+		ret = -EBUSY;
+		goto unlock;
+	}
+
+	if (sysfs_streq(buf, "none")) {
+		led_trigger_remove(led_cdev);
+		goto unlock;
+	}
+
+	if (sysfs_streq(buf, "default")) {
+		led_trigger_set_default(led_cdev);
+		goto unlock;
+	}
+
+	down_read(&triggers_list_lock);
+	list_for_each_entry(trig, &trigger_list, next_trig) {
+		if (sysfs_streq(buf, trig->name) && trigger_relevant(led_cdev, trig)) {
+			down_write(&led_cdev->trigger_lock);
+			led_trigger_set(led_cdev, trig);
+			up_write(&led_cdev->trigger_lock);
+
+			up_read(&triggers_list_lock);
+			goto unlock;
+		}
+	}
+	/* we come here only if buf matches no trigger */
+	ret = -EINVAL;
+	up_read(&triggers_list_lock);
+
+unlock:
+	mutex_unlock(&led_cdev->led_access);
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_trigger_write);
+
+__printf(3, 4)
+static int led_trigger_snprintf(char *buf, ssize_t size, const char *fmt, ...)
+{
+	va_list args;
+	int i;
+
+	va_start(args, fmt);
+	if (size <= 0)
+		i = vsnprintf(NULL, 0, fmt, args);
+	else
+		i = vscnprintf(buf, size, fmt, args);
+	va_end(args);
+
+	return i;
+}
+
+static int led_trigger_format(char *buf, size_t size,
+			      struct led_classdev *led_cdev)
+{
+	struct led_trigger *trig;
+	int len = led_trigger_snprintf(buf, size, "%s",
+				       led_cdev->trigger ? "none" : "[none]");
+
+	if (led_cdev->default_trigger)
+		len += led_trigger_snprintf(buf + len, size - len, " default");
+
+	list_for_each_entry(trig, &trigger_list, next_trig) {
+		bool hit;
+
+		if (!trigger_relevant(led_cdev, trig))
+			continue;
+
+		hit = led_cdev->trigger && !strcmp(led_cdev->trigger->name, trig->name);
+
+		len += led_trigger_snprintf(buf + len, size - len,
+					    " %s%s%s", hit ? "[" : "",
+					    trig->name, hit ? "]" : "");
+	}
+
+	len += led_trigger_snprintf(buf + len, size - len, "\n");
+
+	return len;
+}
+
+/*
+ * It was stupid to create 10000 cpu triggers, but we are stuck with it now.
+ * Don't make that mistake again. We work around it here by creating binary
+ * attribute, which is not limited by length. This is _not_ good design, do not
+ * copy it.
+ */
+ssize_t led_trigger_read(struct file *filp, struct kobject *kobj,
+			const struct bin_attribute *attr, char *buf,
+			loff_t pos, size_t count)
+{
+	struct device *dev = kobj_to_dev(kobj);
+	struct led_classdev *led_cdev = dev_get_drvdata(dev);
+	void *data;
+	int len;
+
+	down_read(&triggers_list_lock);
+	down_read(&led_cdev->trigger_lock);
+
+	len = led_trigger_format(NULL, 0, led_cdev);
+	data = kvmalloc(len + 1, GFP_KERNEL);
+	if (!data) {
+		up_read(&led_cdev->trigger_lock);
+		up_read(&triggers_list_lock);
+		return -ENOMEM;
+	}
+	len = led_trigger_format(data, len + 1, led_cdev);
+
+	up_read(&led_cdev->trigger_lock);
+	up_read(&triggers_list_lock);
+
+	len = memory_read_from_buffer(buf, count, &pos, data, len);
+
+	kvfree(data);
+
+	return len;
+}
+EXPORT_SYMBOL_GPL(led_trigger_read);
+
+/* Caller must ensure led_cdev->trigger_lock held */
+int led_trigger_set(struct led_classdev *led_cdev, struct led_trigger *trig)
+{
+	char *event = NULL;
+	char *envp[2];
+	const char *name;
+	int ret;
+
+	if (!led_cdev->trigger && !trig)
+		return 0;
+
+	name = trig ? trig->name : "none";
+	event = kasprintf(GFP_KERNEL, "TRIGGER=%s", name);
+
+	/* Remove any existing trigger */
+	if (led_cdev->trigger) {
+		spin_lock(&led_cdev->trigger->leddev_list_lock);
+		list_del_rcu(&led_cdev->trig_list);
+		spin_unlock(&led_cdev->trigger->leddev_list_lock);
+
+		/* ensure it's no longer visible on the led_cdevs list */
+		synchronize_rcu();
+
+		cancel_work_sync(&led_cdev->set_brightness_work);
+		led_stop_software_blink(led_cdev);
+		device_remove_groups(led_cdev->dev, led_cdev->trigger->groups);
+		if (led_cdev->trigger->deactivate)
+			led_cdev->trigger->deactivate(led_cdev);
+		led_cdev->trigger = NULL;
+		led_cdev->trigger_data = NULL;
+		led_cdev->activated = false;
+		led_cdev->flags &= ~LED_INIT_DEFAULT_TRIGGER;
+		led_set_brightness(led_cdev, LED_OFF);
+	}
+	if (trig) {
+		spin_lock(&trig->leddev_list_lock);
+		list_add_tail_rcu(&led_cdev->trig_list, &trig->led_cdevs);
+		spin_unlock(&trig->leddev_list_lock);
+		led_cdev->trigger = trig;
+
+		/*
+		 * Some activate() calls use led_trigger_event() to initialize
+		 * the brightness of the LED for which the trigger is being set.
+		 * Ensure the led_cdev is visible on trig->led_cdevs for this.
+		 */
+		synchronize_rcu();
+
+		/*
+		 * If "set brightness to 0" is pending in workqueue,
+		 * we don't want that to be reordered after ->activate()
+		 */
+		flush_work(&led_cdev->set_brightness_work);
+
+		ret = 0;
+		if (trig->activate)
+			ret = trig->activate(led_cdev);
+		else
+			led_set_brightness(led_cdev, trig->brightness);
+		if (ret)
+			goto err_activate;
+
+		ret = device_add_groups(led_cdev->dev, trig->groups);
+		if (ret) {
+			dev_err(led_cdev->dev, "Failed to add trigger attributes\n");
+			goto err_add_groups;
+		}
+	}
+
+	if (event) {
+		envp[0] = event;
+		envp[1] = NULL;
+		if (kobject_uevent_env(&led_cdev->dev->kobj, KOBJ_CHANGE, envp))
+			dev_err(led_cdev->dev,
+				"%s: Error sending uevent\n", __func__);
+		kfree(event);
+	}
+
+	return 0;
+
+err_add_groups:
+
+	if (trig->deactivate)
+		trig->deactivate(led_cdev);
+err_activate:
+
+	spin_lock(&led_cdev->trigger->leddev_list_lock);
+	list_del_rcu(&led_cdev->trig_list);
+	spin_unlock(&led_cdev->trigger->leddev_list_lock);
+	synchronize_rcu();
+	led_cdev->trigger = NULL;
+	led_cdev->trigger_data = NULL;
+	led_set_brightness(led_cdev, LED_OFF);
+	kfree(event);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(led_trigger_set);
+
+void led_trigger_remove(struct led_classdev *led_cdev)
+{
+	down_write(&led_cdev->trigger_lock);
+	led_trigger_set(led_cdev, NULL);
+	up_write(&led_cdev->trigger_lock);
+}
+EXPORT_SYMBOL_GPL(led_trigger_remove);
+
+static bool led_match_default_trigger(struct led_classdev *led_cdev,
+				      struct led_trigger *trig)
+{
+	if (!strcmp(led_cdev->default_trigger, trig->name) &&
+	    trigger_relevant(led_cdev, trig)) {
+		led_cdev->flags |= LED_INIT_DEFAULT_TRIGGER;
+		led_trigger_set(led_cdev, trig);
+		return true;
+	}
+
+	return false;
+}
+
+void led_trigger_set_default(struct led_classdev *led_cdev)
+{
+	struct led_trigger *trig;
+	bool found = false;
+
+	if (!led_cdev->default_trigger)
+		return;
+
+	if (!strcmp(led_cdev->default_trigger, "none")) {
+		led_trigger_remove(led_cdev);
+		return;
+	}
+
+	down_read(&triggers_list_lock);
+	down_write(&led_cdev->trigger_lock);
+	list_for_each_entry(trig, &trigger_list, next_trig) {
+		found = led_match_default_trigger(led_cdev, trig);
+		if (found)
+			break;
+	}
+	up_write(&led_cdev->trigger_lock);
+	up_read(&triggers_list_lock);
+
+	/*
+	 * If default trigger wasn't found, maybe trigger module isn't loaded yet.
+	 * Once loaded it will re-probe with all led_cdev's.
+	 */
+	if (!found)
+		request_module_nowait("ledtrig:%s", led_cdev->default_trigger);
+}
+EXPORT_SYMBOL_GPL(led_trigger_set_default);
+
+/* LED Trigger Interface */
+
+int led_trigger_register(struct led_trigger *trig)
+{
+	struct led_classdev *led_cdev;
+	struct led_trigger *_trig;
+
+	spin_lock_init(&trig->leddev_list_lock);
+	INIT_LIST_HEAD(&trig->led_cdevs);
+
+	down_write(&triggers_list_lock);
+	/* Make sure the trigger's name isn't already in use */
+	list_for_each_entry(_trig, &trigger_list, next_trig) {
+		if (!strcmp(_trig->name, trig->name) &&
+		    (trig->trigger_type == _trig->trigger_type ||
+		     !trig->trigger_type || !_trig->trigger_type)) {
+			up_write(&triggers_list_lock);
+			return -EEXIST;
+		}
+	}
+	/* Add to the list of led triggers */
+	list_add_tail(&trig->next_trig, &trigger_list);
+	up_write(&triggers_list_lock);
+
+	/* Register with any LEDs that have this as a default trigger */
+	down_read(&leds_list_lock);
+	list_for_each_entry(led_cdev, &leds_list, node) {
+		down_write(&led_cdev->trigger_lock);
+		if (!led_cdev->trigger && led_cdev->default_trigger)
+			led_match_default_trigger(led_cdev, trig);
+		up_write(&led_cdev->trigger_lock);
+	}
+	up_read(&leds_list_lock);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(led_trigger_register);
+
+void led_trigger_unregister(struct led_trigger *trig)
+{
+	struct led_classdev *led_cdev;
+
+	if (list_empty_careful(&trig->next_trig))
+		return;
+
+	/* Remove from the list of led triggers */
+	down_write(&triggers_list_lock);
+	list_del_init(&trig->next_trig);
+	up_write(&triggers_list_lock);
+
+	/* Remove anyone actively using this trigger */
+	down_read(&leds_list_lock);
+	list_for_each_entry(led_cdev, &leds_list, node) {
+		down_write(&led_cdev->trigger_lock);
+		if (led_cdev->trigger == trig)
+			led_trigger_set(led_cdev, NULL);
+		up_write(&led_cdev->trigger_lock);
+	}
+	up_read(&leds_list_lock);
+}
+EXPORT_SYMBOL_GPL(led_trigger_unregister);
+
+static void devm_led_trigger_release(struct device *dev, void *res)
+{
+	led_trigger_unregister(*(struct led_trigger **)res);
+}
+
+int devm_led_trigger_register(struct device *dev,
+			      struct led_trigger *trig)
+{
+	struct led_trigger **dr;
+	int rc;
+
+	dr = devres_alloc(devm_led_trigger_release, sizeof(*dr),
+			  GFP_KERNEL);
+	if (!dr)
+		return -ENOMEM;
+
+	*dr = trig;
+
+	rc = led_trigger_register(trig);
+	if (rc)
+		devres_free(dr);
+	else
+		devres_add(dev, dr);
+
+	return rc;
+}
+EXPORT_SYMBOL_GPL(devm_led_trigger_register);
+
+/* Simple LED Trigger Interface */
+
+void led_trigger_event(struct led_trigger *trig,
+			enum led_brightness brightness)
+{
+	struct led_classdev *led_cdev;
+
+	if (!trig)
+		return;
+
+	trig->brightness = brightness;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(led_cdev, &trig->led_cdevs, trig_list)
+		led_set_brightness(led_cdev, brightness);
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(led_trigger_event);
+
+void led_mc_trigger_event(struct led_trigger *trig,
+			  unsigned int *intensity_value, unsigned int num_colors,
+			  enum led_brightness brightness)
+{
+	struct led_classdev *led_cdev;
+
+	if (!trig)
+		return;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(led_cdev, &trig->led_cdevs, trig_list) {
+		if (!(led_cdev->flags & LED_MULTI_COLOR))
+			continue;
+
+		led_mc_set_brightness(led_cdev, intensity_value, num_colors, brightness);
+	}
+	rcu_read_unlock();
+}
+EXPORT_SYMBOL_GPL(led_mc_trigger_event);
+
+static void led_trigger_blink_setup(struct led_trigger *trig,
+			     unsigned long delay_on,
+			     unsigned long delay_off,
+			     int oneshot,
+			     int invert)
+{
+	struct led_classdev *led_cdev;
+
+	if (!trig)
+		return;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(led_cdev, &trig->led_cdevs, trig_list) {
+		if (oneshot)
+			led_blink_set_oneshot(led_cdev, &delay_on, &delay_off,
+					      invert);
+		else
+			led_blink_set_nosleep(led_cdev, delay_on, delay_off);
+	}
+	rcu_read_unlock();
+}
+
+void led_trigger_blink(struct led_trigger *trig,
+		       unsigned long delay_on,
+		       unsigned long delay_off)
+{
+	led_trigger_blink_setup(trig, delay_on, delay_off, 0, 0);
+}
+EXPORT_SYMBOL_GPL(led_trigger_blink);
+
+void led_trigger_blink_oneshot(struct led_trigger *trig,
+			       unsigned long delay_on,
+			       unsigned long delay_off,
+			       int invert)
+{
+	led_trigger_blink_setup(trig, delay_on, delay_off, 1, invert);
+}
+EXPORT_SYMBOL_GPL(led_trigger_blink_oneshot);
+
+void led_trigger_register_simple(const char *name, struct led_trigger **tp)
+{
+	struct led_trigger *trig;
+	int err;
+
+	trig = kzalloc_obj(struct led_trigger);
+
+	if (trig) {
+		trig->name = name;
+		err = led_trigger_register(trig);
+		if (err < 0) {
+			kfree(trig);
+			trig = NULL;
+			pr_warn("LED trigger %s failed to register (%d)\n",
+				name, err);
+		}
+	} else {
+		pr_warn("LED trigger %s failed to register (no memory)\n",
+			name);
+	}
+	*tp = trig;
+}
+EXPORT_SYMBOL_GPL(led_trigger_register_simple);
+
+void led_trigger_unregister_simple(struct led_trigger *trig)
+{
+	if (trig)
+		led_trigger_unregister(trig);
+	kfree(trig);
+}
+EXPORT_SYMBOL_GPL(led_trigger_unregister_simple);