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, 165 insertions, 0 deletions

diff --git a/drivers/leds/trigger/ledtrig-input-events.c b/drivers/leds/trigger/ledtrig-input-events.c
new file mode 100644
index 000000000..d057b2a23
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-input-events.c
@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Input Events LED trigger
+ *
+ * Copyright (C) 2024 Hans de Goede <hansg@kernel.org>
+ */
+
+#include <linux/input.h>
+#include <linux/jiffies.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/workqueue.h>
+#include "../leds.h"
+
+static unsigned long led_off_delay_ms = 5000;
+module_param(led_off_delay_ms, ulong, 0644);
+MODULE_PARM_DESC(led_off_delay_ms,
+	"Specify delay in ms for turning LEDs off after last input event");
+
+static struct input_events_data {
+	struct delayed_work work;
+	spinlock_t lock;
+	/* To avoid repeatedly setting the brightness while there are events */
+	bool led_on;
+	unsigned long led_off_time;
+} input_events_data;
+
+static struct led_trigger *input_events_led_trigger;
+
+static void led_input_events_work(struct work_struct *work)
+{
+	struct input_events_data *data =
+		container_of(work, struct input_events_data, work.work);
+
+	spin_lock_irq(&data->lock);
+
+	/*
+	 * This time_after_eq() check avoids a race where this work starts
+	 * running before a new event pushed led_off_time back.
+	 */
+	if (time_after_eq(jiffies, data->led_off_time)) {
+		led_trigger_event(input_events_led_trigger, LED_OFF);
+		data->led_on = false;
+	}
+
+	spin_unlock_irq(&data->lock);
+}
+
+static void input_events_event(struct input_handle *handle, unsigned int type,
+			       unsigned int code, int val)
+{
+	struct input_events_data *data = &input_events_data;
+	unsigned long led_off_delay = msecs_to_jiffies(led_off_delay_ms);
+	unsigned long flags;
+
+	spin_lock_irqsave(&data->lock, flags);
+
+	if (!data->led_on) {
+		led_trigger_event(input_events_led_trigger, LED_FULL);
+		data->led_on = true;
+	}
+	data->led_off_time = jiffies + led_off_delay;
+
+	spin_unlock_irqrestore(&data->lock, flags);
+
+	mod_delayed_work(system_percpu_wq, &data->work, led_off_delay);
+}
+
+static int input_events_connect(struct input_handler *handler, struct input_dev *dev,
+				const struct input_device_id *id)
+{
+	struct input_handle *handle;
+	int ret;
+
+	handle = kzalloc_obj(*handle);
+	if (!handle)
+		return -ENOMEM;
+
+	handle->dev = dev;
+	handle->handler = handler;
+	handle->name = KBUILD_MODNAME;
+
+	ret = input_register_handle(handle);
+	if (ret)
+		goto err_free_handle;
+
+	ret = input_open_device(handle);
+	if (ret)
+		goto err_unregister_handle;
+
+	return 0;
+
+err_unregister_handle:
+	input_unregister_handle(handle);
+err_free_handle:
+	kfree(handle);
+	return ret;
+}
+
+static void input_events_disconnect(struct input_handle *handle)
+{
+	input_close_device(handle);
+	input_unregister_handle(handle);
+	kfree(handle);
+}
+
+static const struct input_device_id input_events_ids[] = {
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+		.evbit = { BIT_MASK(EV_KEY) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+		.evbit = { BIT_MASK(EV_REL) },
+	},
+	{
+		.flags = INPUT_DEVICE_ID_MATCH_EVBIT,
+		.evbit = { BIT_MASK(EV_ABS) },
+	},
+	{ }
+};
+
+static struct input_handler input_events_handler = {
+	.name = KBUILD_MODNAME,
+	.event = input_events_event,
+	.connect = input_events_connect,
+	.disconnect = input_events_disconnect,
+	.id_table = input_events_ids,
+};
+
+static int __init input_events_init(void)
+{
+	int ret;
+
+	INIT_DELAYED_WORK(&input_events_data.work, led_input_events_work);
+	spin_lock_init(&input_events_data.lock);
+
+	led_trigger_register_simple("input-events", &input_events_led_trigger);
+
+	ret = input_register_handler(&input_events_handler);
+	if (ret) {
+		led_trigger_unregister_simple(input_events_led_trigger);
+		return ret;
+	}
+
+	return 0;
+}
+
+static void __exit input_events_exit(void)
+{
+	input_unregister_handler(&input_events_handler);
+	cancel_delayed_work_sync(&input_events_data.work);
+	led_trigger_unregister_simple(input_events_led_trigger);
+}
+
+module_init(input_events_init);
+module_exit(input_events_exit);
+
+MODULE_AUTHOR("Hans de Goede <hansg@kernel.org>");
+MODULE_DESCRIPTION("Input Events LED trigger");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ledtrig:input-events");