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, 357 insertions, 0 deletions

diff --git a/drivers/leds/trigger/ledtrig-tty.c b/drivers/leds/trigger/ledtrig-tty.c
new file mode 100644
index 000000000..372557114
--- /dev/null
+++ b/drivers/leds/trigger/ledtrig-tty.c
@@ -0,0 +1,357 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <linux/completion.h>
+#include <linux/delay.h>
+#include <linux/leds.h>
+#include <linux/module.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <uapi/linux/serial.h>
+
+#define LEDTRIG_TTY_INTERVAL	50
+
+struct ledtrig_tty_data {
+	struct led_classdev *led_cdev;
+	struct delayed_work dwork;
+	struct completion sysfs;
+	const char *ttyname;
+	struct tty_struct *tty;
+	int rx, tx;
+	bool mode_rx;
+	bool mode_tx;
+	bool mode_cts;
+	bool mode_dsr;
+	bool mode_dcd;
+	bool mode_rng;
+};
+
+/* Indicates which state the LED should now display */
+enum led_trigger_tty_state {
+	TTY_LED_BLINK,
+	TTY_LED_ENABLE,
+	TTY_LED_DISABLE,
+};
+
+enum led_trigger_tty_modes {
+	TRIGGER_TTY_RX = 0,
+	TRIGGER_TTY_TX,
+	TRIGGER_TTY_CTS,
+	TRIGGER_TTY_DSR,
+	TRIGGER_TTY_DCD,
+	TRIGGER_TTY_RNG,
+};
+
+static int ledtrig_tty_wait_for_completion(struct device *dev)
+{
+	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+	int ret;
+
+	ret = wait_for_completion_timeout(&trigger_data->sysfs,
+					  msecs_to_jiffies(LEDTRIG_TTY_INTERVAL * 20));
+	if (ret == 0)
+		return -ETIMEDOUT;
+
+	return ret;
+}
+
+static ssize_t ttyname_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+	ssize_t len = 0;
+	int completion;
+
+	reinit_completion(&trigger_data->sysfs);
+	completion = ledtrig_tty_wait_for_completion(dev);
+	if (completion < 0)
+		return completion;
+
+	if (trigger_data->ttyname)
+		len = sprintf(buf, "%s\n", trigger_data->ttyname);
+
+	return len;
+}
+
+static ssize_t ttyname_store(struct device *dev,
+			     struct device_attribute *attr, const char *buf,
+			     size_t size)
+{
+	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+	char *ttyname;
+	ssize_t ret = size;
+	int completion;
+
+	if (size > 0 && buf[size - 1] == '\n')
+		size -= 1;
+
+	if (size) {
+		ttyname = kmemdup_nul(buf, size, GFP_KERNEL);
+		if (!ttyname)
+			return -ENOMEM;
+	} else {
+		ttyname = NULL;
+	}
+
+	reinit_completion(&trigger_data->sysfs);
+	completion = ledtrig_tty_wait_for_completion(dev);
+	if (completion < 0)
+		return completion;
+
+	kfree(trigger_data->ttyname);
+	tty_kref_put(trigger_data->tty);
+	trigger_data->tty = NULL;
+
+	trigger_data->ttyname = ttyname;
+
+	return ret;
+}
+static DEVICE_ATTR_RW(ttyname);
+
+static ssize_t ledtrig_tty_attr_show(struct device *dev, char *buf,
+				     enum led_trigger_tty_modes attr)
+{
+	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+	bool state;
+
+	switch (attr) {
+	case TRIGGER_TTY_RX:
+		state = trigger_data->mode_rx;
+		break;
+	case TRIGGER_TTY_TX:
+		state = trigger_data->mode_tx;
+		break;
+	case TRIGGER_TTY_CTS:
+		state = trigger_data->mode_cts;
+		break;
+	case TRIGGER_TTY_DSR:
+		state = trigger_data->mode_dsr;
+		break;
+	case TRIGGER_TTY_DCD:
+		state = trigger_data->mode_dcd;
+		break;
+	case TRIGGER_TTY_RNG:
+		state = trigger_data->mode_rng;
+		break;
+	}
+
+	return sysfs_emit(buf, "%u\n", state);
+}
+
+static ssize_t ledtrig_tty_attr_store(struct device *dev, const char *buf,
+				      size_t size, enum led_trigger_tty_modes attr)
+{
+	struct ledtrig_tty_data *trigger_data = led_trigger_get_drvdata(dev);
+	bool state;
+	int ret;
+
+	ret = kstrtobool(buf, &state);
+	if (ret)
+		return ret;
+
+	switch (attr) {
+	case TRIGGER_TTY_RX:
+		trigger_data->mode_rx = state;
+		break;
+	case TRIGGER_TTY_TX:
+		trigger_data->mode_tx = state;
+		break;
+	case TRIGGER_TTY_CTS:
+		trigger_data->mode_cts = state;
+		break;
+	case TRIGGER_TTY_DSR:
+		trigger_data->mode_dsr = state;
+		break;
+	case TRIGGER_TTY_DCD:
+		trigger_data->mode_dcd = state;
+		break;
+	case TRIGGER_TTY_RNG:
+		trigger_data->mode_rng = state;
+		break;
+	}
+
+	return size;
+}
+
+#define DEFINE_TTY_TRIGGER(trigger_name, trigger) \
+	static ssize_t trigger_name##_show(struct device *dev, \
+		struct device_attribute *attr, char *buf) \
+	{ \
+		return ledtrig_tty_attr_show(dev, buf, trigger); \
+	} \
+	static ssize_t trigger_name##_store(struct device *dev, \
+		struct device_attribute *attr, const char *buf, size_t size) \
+	{ \
+		return ledtrig_tty_attr_store(dev, buf, size, trigger); \
+	} \
+	static DEVICE_ATTR_RW(trigger_name)
+
+DEFINE_TTY_TRIGGER(rx, TRIGGER_TTY_RX);
+DEFINE_TTY_TRIGGER(tx, TRIGGER_TTY_TX);
+DEFINE_TTY_TRIGGER(cts, TRIGGER_TTY_CTS);
+DEFINE_TTY_TRIGGER(dsr, TRIGGER_TTY_DSR);
+DEFINE_TTY_TRIGGER(dcd, TRIGGER_TTY_DCD);
+DEFINE_TTY_TRIGGER(rng, TRIGGER_TTY_RNG);
+
+static void ledtrig_tty_work(struct work_struct *work)
+{
+	struct ledtrig_tty_data *trigger_data =
+		container_of(work, struct ledtrig_tty_data, dwork.work);
+	enum led_trigger_tty_state state = TTY_LED_DISABLE;
+	unsigned long interval = LEDTRIG_TTY_INTERVAL;
+	bool invert = false;
+	int status;
+	int ret;
+
+	if (!trigger_data->ttyname)
+		goto out;
+
+	/* try to get the tty corresponding to $ttyname */
+	if (!trigger_data->tty) {
+		dev_t devno;
+		struct tty_struct *tty;
+		int ret;
+
+		ret = tty_dev_name_to_number(trigger_data->ttyname, &devno);
+		if (ret < 0)
+			/*
+			 * A device with this name might appear later, so keep
+			 * retrying.
+			 */
+			goto out;
+
+		tty = tty_kopen_shared(devno);
+		if (IS_ERR_OR_NULL(tty))
+			/* What to do? retry or abort */
+			goto out;
+
+		trigger_data->tty = tty;
+	}
+
+	status = tty_get_tiocm(trigger_data->tty);
+	if (status > 0) {
+		if (trigger_data->mode_cts) {
+			if (status & TIOCM_CTS)
+				state = TTY_LED_ENABLE;
+		}
+
+		if (trigger_data->mode_dsr) {
+			if (status & TIOCM_DSR)
+				state = TTY_LED_ENABLE;
+		}
+
+		if (trigger_data->mode_dcd) {
+			if (status & TIOCM_CAR)
+				state = TTY_LED_ENABLE;
+		}
+
+		if (trigger_data->mode_rng) {
+			if (status & TIOCM_RNG)
+				state = TTY_LED_ENABLE;
+		}
+	}
+
+	/*
+	 * The evaluation of rx/tx must be done after the evaluation
+	 * of TIOCM_*, because rx/tx has priority.
+	 */
+	if (trigger_data->mode_rx || trigger_data->mode_tx) {
+		struct serial_icounter_struct icount;
+
+		ret = tty_get_icount(trigger_data->tty, &icount);
+		if (ret)
+			goto out;
+
+		if (trigger_data->mode_tx && (icount.tx != trigger_data->tx)) {
+			trigger_data->tx = icount.tx;
+			invert = state == TTY_LED_ENABLE;
+			state = TTY_LED_BLINK;
+		}
+
+		if (trigger_data->mode_rx && (icount.rx != trigger_data->rx)) {
+			trigger_data->rx = icount.rx;
+			invert = state == TTY_LED_ENABLE;
+			state = TTY_LED_BLINK;
+		}
+	}
+
+out:
+	switch (state) {
+	case TTY_LED_BLINK:
+		led_blink_set_oneshot(trigger_data->led_cdev, &interval,
+				&interval, invert);
+		break;
+	case TTY_LED_ENABLE:
+		led_set_brightness(trigger_data->led_cdev,
+				trigger_data->led_cdev->blink_brightness);
+		break;
+	case TTY_LED_DISABLE:
+		fallthrough;
+	default:
+		led_set_brightness(trigger_data->led_cdev, LED_OFF);
+		break;
+	}
+
+	complete_all(&trigger_data->sysfs);
+	schedule_delayed_work(&trigger_data->dwork,
+			      msecs_to_jiffies(LEDTRIG_TTY_INTERVAL * 2));
+}
+
+static struct attribute *ledtrig_tty_attrs[] = {
+	&dev_attr_ttyname.attr,
+	&dev_attr_rx.attr,
+	&dev_attr_tx.attr,
+	&dev_attr_cts.attr,
+	&dev_attr_dsr.attr,
+	&dev_attr_dcd.attr,
+	&dev_attr_rng.attr,
+	NULL
+};
+ATTRIBUTE_GROUPS(ledtrig_tty);
+
+static int ledtrig_tty_activate(struct led_classdev *led_cdev)
+{
+	struct ledtrig_tty_data *trigger_data;
+
+	trigger_data = kzalloc_obj(*trigger_data);
+	if (!trigger_data)
+		return -ENOMEM;
+
+	/* Enable default rx/tx mode */
+	trigger_data->mode_rx = true;
+	trigger_data->mode_tx = true;
+
+	led_set_trigger_data(led_cdev, trigger_data);
+
+	INIT_DELAYED_WORK(&trigger_data->dwork, ledtrig_tty_work);
+	trigger_data->led_cdev = led_cdev;
+	init_completion(&trigger_data->sysfs);
+
+	schedule_delayed_work(&trigger_data->dwork, 0);
+
+	return 0;
+}
+
+static void ledtrig_tty_deactivate(struct led_classdev *led_cdev)
+{
+	struct ledtrig_tty_data *trigger_data = led_get_trigger_data(led_cdev);
+
+	cancel_delayed_work_sync(&trigger_data->dwork);
+
+	kfree(trigger_data->ttyname);
+	tty_kref_put(trigger_data->tty);
+	trigger_data->tty = NULL;
+
+	kfree(trigger_data);
+}
+
+static struct led_trigger ledtrig_tty = {
+	.name = "tty",
+	.activate = ledtrig_tty_activate,
+	.deactivate = ledtrig_tty_deactivate,
+	.groups = ledtrig_tty_groups,
+};
+module_led_trigger(ledtrig_tty);
+
+MODULE_AUTHOR("Uwe Kleine-König <u.kleine-koenig@pengutronix.de>");
+MODULE_DESCRIPTION("UART LED trigger");
+MODULE_LICENSE("GPL v2");