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, 198 insertions, 0 deletions

diff --git a/drivers/leds/trigger/ledtrig-transient.c b/drivers/leds/trigger/ledtrig-transient.c
new file mode 100644
index 000000000..8d928bb2a
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-transient.c
@@ -0,0 +1,198 @@
+// SPDX-License-Identifier: GPL-2.0
+//
+// LED Kernel Transient Trigger
+//
+// Transient trigger allows one shot timer activation. Please refer to
+// Documentation/leds/ledtrig-transient.rst for details
+// Copyright (C) 2012 Shuah Khan <shuahkhan@gmail.com>
+//
+// Based on Richard Purdie's ledtrig-timer.c and Atsushi Nemoto's
+// ledtrig-heartbeat.c
+// Design and use-case input from Jonas Bonn <jonas@southpole.se> and
+// Neil Brown <neilb@suse.de>
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/slab.h>
+#include <linux/timer.h>
+#include <linux/leds.h>
+#include "../leds.h"
+
+struct transient_trig_data {
+	int activate;
+	int state;
+	int restore_state;
+	unsigned long duration;
+	struct timer_list timer;
+	struct led_classdev *led_cdev;
+};
+
+static void transient_timer_function(struct timer_list *t)
+{
+	struct transient_trig_data *transient_data =
+		timer_container_of(transient_data, t, timer);
+	struct led_classdev *led_cdev = transient_data->led_cdev;
+
+	transient_data->activate = 0;
+	led_set_brightness_nosleep(led_cdev, transient_data->restore_state);
+}
+
+static ssize_t transient_activate_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct transient_trig_data *transient_data =
+		led_trigger_get_drvdata(dev);
+
+	return sprintf(buf, "%d\n", transient_data->activate);
+}
+
+static ssize_t transient_activate_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = led_trigger_get_led(dev);
+	struct transient_trig_data *transient_data =
+		led_trigger_get_drvdata(dev);
+	unsigned long state;
+	ssize_t ret;
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		return ret;
+
+	if (state != 1 && state != 0)
+		return -EINVAL;
+
+	/* cancel the running timer */
+	if (state == 0 && transient_data->activate == 1) {
+		timer_delete(&transient_data->timer);
+		transient_data->activate = state;
+		led_set_brightness_nosleep(led_cdev,
+					transient_data->restore_state);
+		return size;
+	}
+
+	/* start timer if there is no active timer */
+	if (state == 1 && transient_data->activate == 0 &&
+	    transient_data->duration != 0) {
+		transient_data->activate = state;
+		led_set_brightness_nosleep(led_cdev, transient_data->state);
+		transient_data->restore_state =
+		    (transient_data->state == LED_FULL) ? LED_OFF : LED_FULL;
+		mod_timer(&transient_data->timer,
+			  jiffies + msecs_to_jiffies(transient_data->duration));
+	}
+
+	/* state == 0 && transient_data->activate == 0
+		timer is not active - just return */
+	/* state == 1 && transient_data->activate == 1
+		timer is already active - just return */
+
+	return size;
+}
+
+static ssize_t transient_duration_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct transient_trig_data *transient_data = led_trigger_get_drvdata(dev);
+
+	return sprintf(buf, "%lu\n", transient_data->duration);
+}
+
+static ssize_t transient_duration_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct transient_trig_data *transient_data =
+		led_trigger_get_drvdata(dev);
+	unsigned long state;
+	ssize_t ret;
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		return ret;
+
+	transient_data->duration = state;
+	return size;
+}
+
+static ssize_t transient_state_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct transient_trig_data *transient_data =
+		led_trigger_get_drvdata(dev);
+	int state;
+
+	state = (transient_data->state == LED_FULL) ? 1 : 0;
+	return sprintf(buf, "%d\n", state);
+}
+
+static ssize_t transient_state_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct transient_trig_data *transient_data =
+		led_trigger_get_drvdata(dev);
+	unsigned long state;
+	ssize_t ret;
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		return ret;
+
+	if (state != 1 && state != 0)
+		return -EINVAL;
+
+	transient_data->state = (state == 1) ? LED_FULL : LED_OFF;
+	return size;
+}
+
+static DEVICE_ATTR(activate, 0644, transient_activate_show,
+		   transient_activate_store);
+static DEVICE_ATTR(duration, 0644, transient_duration_show,
+		   transient_duration_store);
+static DEVICE_ATTR(state, 0644, transient_state_show, transient_state_store);
+
+static struct attribute *transient_trig_attrs[] = {
+	&dev_attr_activate.attr,
+	&dev_attr_duration.attr,
+	&dev_attr_state.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(transient_trig);
+
+static int transient_trig_activate(struct led_classdev *led_cdev)
+{
+	struct transient_trig_data *tdata;
+
+	tdata = kzalloc_obj(struct transient_trig_data);
+	if (!tdata)
+		return -ENOMEM;
+
+	led_set_trigger_data(led_cdev, tdata);
+	tdata->led_cdev = led_cdev;
+
+	timer_setup(&tdata->timer, transient_timer_function, 0);
+
+	return 0;
+}
+
+static void transient_trig_deactivate(struct led_classdev *led_cdev)
+{
+	struct transient_trig_data *transient_data = led_get_trigger_data(led_cdev);
+
+	timer_shutdown_sync(&transient_data->timer);
+	led_set_brightness_nosleep(led_cdev, transient_data->restore_state);
+	kfree(transient_data);
+}
+
+static struct led_trigger transient_trigger = {
+	.name     = "transient",
+	.activate = transient_trig_activate,
+	.deactivate = transient_trig_deactivate,
+	.groups = transient_trig_groups,
+};
+module_led_trigger(transient_trigger);
+
+MODULE_AUTHOR("Shuah Khan <shuahkhan@gmail.com>");
+MODULE_DESCRIPTION("Transient LED trigger");
+MODULE_LICENSE("GPL v2");