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, 135 insertions, 0 deletions

diff --git a/drivers/leds/trigger/ledtrig-timer.c b/drivers/leds/trigger/ledtrig-timer.c
new file mode 100644
index 000000000..1d213c999
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-timer.c
@@ -0,0 +1,135 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * LED Kernel Timer Trigger
+ *
+ * Copyright 2005-2006 Openedhand Ltd.
+ *
+ * Author: Richard Purdie <rpurdie@openedhand.com>
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/device.h>
+#include <linux/ctype.h>
+#include <linux/slab.h>
+#include <linux/leds.h>
+
+static ssize_t led_delay_on_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = led_trigger_get_led(dev);
+
+	return sprintf(buf, "%lu\n", led_cdev->blink_delay_on);
+}
+
+static ssize_t led_delay_on_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = led_trigger_get_led(dev);
+	unsigned long state;
+	ssize_t ret;
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		return ret;
+
+	led_blink_set(led_cdev, &state, &led_cdev->blink_delay_off);
+	led_cdev->blink_delay_on = state;
+
+	return size;
+}
+
+static ssize_t led_delay_off_show(struct device *dev,
+		struct device_attribute *attr, char *buf)
+{
+	struct led_classdev *led_cdev = led_trigger_get_led(dev);
+
+	return sprintf(buf, "%lu\n", led_cdev->blink_delay_off);
+}
+
+static ssize_t led_delay_off_store(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t size)
+{
+	struct led_classdev *led_cdev = led_trigger_get_led(dev);
+	unsigned long state;
+	ssize_t ret;
+
+	ret = kstrtoul(buf, 10, &state);
+	if (ret)
+		return ret;
+
+	led_blink_set(led_cdev, &led_cdev->blink_delay_on, &state);
+	led_cdev->blink_delay_off = state;
+
+	return size;
+}
+
+static DEVICE_ATTR(delay_on, 0644, led_delay_on_show, led_delay_on_store);
+static DEVICE_ATTR(delay_off, 0644, led_delay_off_show, led_delay_off_store);
+
+static struct attribute *timer_trig_attrs[] = {
+	&dev_attr_delay_on.attr,
+	&dev_attr_delay_off.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(timer_trig);
+
+static void pattern_init(struct led_classdev *led_cdev)
+{
+	u32 *pattern;
+	unsigned int size = 0;
+
+	pattern = led_get_default_pattern(led_cdev, &size);
+	if (!pattern)
+		return;
+
+	if (size != 2) {
+		dev_warn(led_cdev->dev,
+			 "Expected 2 but got %u values for delays pattern\n",
+			 size);
+		goto out;
+	}
+
+	led_cdev->blink_delay_on = pattern[0];
+	led_cdev->blink_delay_off = pattern[1];
+	/* led_blink_set() called by caller */
+
+out:
+	kfree(pattern);
+}
+
+static int timer_trig_activate(struct led_classdev *led_cdev)
+{
+	if (led_cdev->flags & LED_INIT_DEFAULT_TRIGGER) {
+		pattern_init(led_cdev);
+		/*
+		 * Mark as initialized even on pattern_init() error because
+		 * any consecutive call to it would produce the same error.
+		 */
+		led_cdev->flags &= ~LED_INIT_DEFAULT_TRIGGER;
+	}
+
+	led_blink_set(led_cdev, &led_cdev->blink_delay_on,
+		      &led_cdev->blink_delay_off);
+
+	return 0;
+}
+
+static void timer_trig_deactivate(struct led_classdev *led_cdev)
+{
+	/* Stop blinking */
+	led_set_brightness(led_cdev, LED_OFF);
+}
+
+static struct led_trigger timer_led_trigger = {
+	.name     = "timer",
+	.activate = timer_trig_activate,
+	.deactivate = timer_trig_deactivate,
+	.groups = timer_trig_groups,
+};
+module_led_trigger(timer_led_trigger);
+
+MODULE_AUTHOR("Richard Purdie <rpurdie@openedhand.com>");
+MODULE_DESCRIPTION("Timer LED trigger");
+MODULE_LICENSE("GPL v2");