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, 191 insertions, 0 deletions

diff --git a/drivers/usb/serial/symbolserial.c b/drivers/usb/serial/symbolserial.c
new file mode 100644
index 000000000..8823671a9
--- /dev/null
+++ b/drivers/usb/serial/symbolserial.c
@@ -0,0 +1,191 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Symbol USB barcode to serial driver
+ *
+ * Copyright (C) 2013 Johan Hovold <jhovold@gmail.com>
+ * Copyright (C) 2009 Greg Kroah-Hartman <gregkh@suse.de>
+ * Copyright (C) 2009 Novell Inc.
+ */
+
+#include <linux/kernel.h>
+#include <linux/tty.h>
+#include <linux/slab.h>
+#include <linux/tty_flip.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(0x05e0, 0x0600) },
+	{ },
+};
+MODULE_DEVICE_TABLE(usb, id_table);
+
+struct symbol_private {
+	spinlock_t lock;	/* protects the following flags */
+	bool throttled;
+	bool actually_throttled;
+};
+
+static void symbol_int_callback(struct urb *urb)
+{
+	struct usb_serial_port *port = urb->context;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	unsigned char *data = urb->transfer_buffer;
+	int status = urb->status;
+	unsigned long flags;
+	int result;
+	int data_length;
+
+	switch (status) {
+	case 0:
+		/* success */
+		break;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		/* this urb is terminated, clean up */
+		dev_dbg(&port->dev, "%s - urb shutting down with status: %d\n",
+			__func__, status);
+		return;
+	default:
+		dev_dbg(&port->dev, "%s - nonzero urb status received: %d\n",
+			__func__, status);
+		goto exit;
+	}
+
+	usb_serial_debug_data(&port->dev, __func__, urb->actual_length, data);
+
+	/*
+	 * Data from the device comes with a 1 byte header:
+	 *
+	 * <size of data> <data>...
+	 */
+	if (urb->actual_length > 1) {
+		data_length = data[0];
+		if (data_length > (urb->actual_length - 1))
+			data_length = urb->actual_length - 1;
+		tty_insert_flip_string(&port->port, &data[1], data_length);
+		tty_flip_buffer_push(&port->port);
+	} else {
+		dev_dbg(&port->dev, "%s - short packet\n", __func__);
+	}
+
+exit:
+	spin_lock_irqsave(&priv->lock, flags);
+
+	/* Continue trying to always read if we should */
+	if (!priv->throttled) {
+		result = usb_submit_urb(port->interrupt_in_urb, GFP_ATOMIC);
+		if (result)
+			dev_err(&port->dev,
+			    "%s - failed resubmitting read urb, error %d\n",
+							__func__, result);
+	} else
+		priv->actually_throttled = true;
+	spin_unlock_irqrestore(&priv->lock, flags);
+}
+
+static int symbol_open(struct tty_struct *tty, struct usb_serial_port *port)
+{
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	unsigned long flags;
+	int result = 0;
+
+	spin_lock_irqsave(&priv->lock, flags);
+	priv->throttled = false;
+	priv->actually_throttled = false;
+	spin_unlock_irqrestore(&priv->lock, flags);
+
+	/* Start reading from the device */
+	result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
+	if (result)
+		dev_err(&port->dev,
+			"%s - failed resubmitting read urb, error %d\n",
+			__func__, result);
+	return result;
+}
+
+static void symbol_close(struct usb_serial_port *port)
+{
+	usb_kill_urb(port->interrupt_in_urb);
+}
+
+static void symbol_throttle(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+
+	spin_lock_irq(&priv->lock);
+	priv->throttled = true;
+	spin_unlock_irq(&priv->lock);
+}
+
+static void symbol_unthrottle(struct tty_struct *tty)
+{
+	struct usb_serial_port *port = tty->driver_data;
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+	int result;
+	bool was_throttled;
+
+	spin_lock_irq(&priv->lock);
+	priv->throttled = false;
+	was_throttled = priv->actually_throttled;
+	priv->actually_throttled = false;
+	spin_unlock_irq(&priv->lock);
+
+	if (was_throttled) {
+		result = usb_submit_urb(port->interrupt_in_urb, GFP_KERNEL);
+		if (result)
+			dev_err(&port->dev,
+				"%s - failed submitting read urb, error %d\n",
+							__func__, result);
+	}
+}
+
+static int symbol_port_probe(struct usb_serial_port *port)
+{
+	struct symbol_private *priv;
+
+	priv = kzalloc_obj(*priv);
+	if (!priv)
+		return -ENOMEM;
+
+	spin_lock_init(&priv->lock);
+
+	usb_set_serial_port_data(port, priv);
+
+	return 0;
+}
+
+static void symbol_port_remove(struct usb_serial_port *port)
+{
+	struct symbol_private *priv = usb_get_serial_port_data(port);
+
+	kfree(priv);
+}
+
+static struct usb_serial_driver symbol_device = {
+	.driver = {
+		.name =		"symbol",
+	},
+	.id_table =		id_table,
+	.num_ports =		1,
+	.num_interrupt_in =	1,
+	.port_probe =		symbol_port_probe,
+	.port_remove =		symbol_port_remove,
+	.open =			symbol_open,
+	.close =		symbol_close,
+	.throttle = 		symbol_throttle,
+	.unthrottle =		symbol_unthrottle,
+	.read_int_callback =	symbol_int_callback,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&symbol_device, NULL
+};
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_DESCRIPTION("Symbol USB barcode to serial driver");
+MODULE_LICENSE("GPL v2");