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, 275 insertions, 0 deletions

diff --git a/drivers/input/joystick/pxrc.c b/drivers/input/joystick/pxrc.c
new file mode 100644
index 000000000..52d9eab66
--- /dev/null
+++ b/drivers/input/joystick/pxrc.c
@@ -0,0 +1,275 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Driver for Phoenix RC Flight Controller Adapter
+ *
+ * Copyright (C) 2018 Marcus Folkesson <marcus.folkesson@gmail.com>
+ */
+
+#include <linux/cleanup.h>
+#include <linux/errno.h>
+#include <linux/input.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mutex.h>
+#include <linux/slab.h>
+#include <linux/uaccess.h>
+
+#include <linux/usb.h>
+#include <linux/usb/input.h>
+
+#define PXRC_VENDOR_ID		0x1781
+#define PXRC_PRODUCT_ID		0x0898
+
+struct pxrc {
+	struct input_dev	*input;
+	struct usb_interface	*intf;
+	struct urb		*urb;
+	struct mutex		pm_mutex;
+	bool			is_open;
+	char			phys[64];
+};
+
+static void pxrc_usb_irq(struct urb *urb)
+{
+	struct pxrc *pxrc = urb->context;
+	u8 *data = urb->transfer_buffer;
+	int error;
+
+	switch (urb->status) {
+	case 0:
+		/* success */
+		break;
+	case -ETIME:
+		/* this urb is timing out */
+		dev_dbg(&pxrc->intf->dev,
+			"%s - urb timed out - was the device unplugged?\n",
+			__func__);
+		return;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+	case -EPIPE:
+		/* this urb is terminated, clean up */
+		dev_dbg(&pxrc->intf->dev, "%s - urb shutting down with status: %d\n",
+			__func__, urb->status);
+		return;
+	default:
+		dev_dbg(&pxrc->intf->dev, "%s - nonzero urb status received: %d\n",
+			__func__, urb->status);
+		goto exit;
+	}
+
+	if (urb->actual_length == 8) {
+		input_report_abs(pxrc->input, ABS_X, data[0]);
+		input_report_abs(pxrc->input, ABS_Y, data[2]);
+		input_report_abs(pxrc->input, ABS_RX, data[3]);
+		input_report_abs(pxrc->input, ABS_RY, data[4]);
+		input_report_abs(pxrc->input, ABS_RUDDER, data[5]);
+		input_report_abs(pxrc->input, ABS_THROTTLE, data[6]);
+		input_report_abs(pxrc->input, ABS_MISC, data[7]);
+
+		input_report_key(pxrc->input, BTN_A, data[1]);
+	}
+
+exit:
+	/* Resubmit to fetch new fresh URBs */
+	error = usb_submit_urb(urb, GFP_ATOMIC);
+	if (error && error != -EPERM)
+		dev_err(&pxrc->intf->dev,
+			"%s - usb_submit_urb failed with result: %d",
+			__func__, error);
+}
+
+static int pxrc_open(struct input_dev *input)
+{
+	struct pxrc *pxrc = input_get_drvdata(input);
+	int error;
+
+	guard(mutex)(&pxrc->pm_mutex);
+	error = usb_submit_urb(pxrc->urb, GFP_KERNEL);
+	if (error) {
+		dev_err(&pxrc->intf->dev,
+			"%s - usb_submit_urb failed, error: %d\n",
+			__func__, error);
+		return -EIO;
+	}
+
+	pxrc->is_open = true;
+	return 0;
+}
+
+static void pxrc_close(struct input_dev *input)
+{
+	struct pxrc *pxrc = input_get_drvdata(input);
+
+	guard(mutex)(&pxrc->pm_mutex);
+	usb_kill_urb(pxrc->urb);
+	pxrc->is_open = false;
+}
+
+static void pxrc_free_urb(void *_pxrc)
+{
+	struct pxrc *pxrc = _pxrc;
+
+	usb_free_urb(pxrc->urb);
+}
+
+static int pxrc_probe(struct usb_interface *intf,
+		      const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(intf);
+	struct pxrc *pxrc;
+	struct usb_endpoint_descriptor *epirq;
+	size_t xfer_size;
+	void *xfer_buf;
+	int error;
+
+	/*
+	 * Locate the endpoint information. This device only has an
+	 * interrupt endpoint.
+	 */
+	error = usb_find_common_endpoints(intf->cur_altsetting,
+					  NULL, NULL, &epirq, NULL);
+	if (error) {
+		dev_err(&intf->dev, "Could not find endpoint\n");
+		return error;
+	}
+
+	pxrc = devm_kzalloc(&intf->dev, sizeof(*pxrc), GFP_KERNEL);
+	if (!pxrc)
+		return -ENOMEM;
+
+	mutex_init(&pxrc->pm_mutex);
+	pxrc->intf = intf;
+
+	usb_set_intfdata(pxrc->intf, pxrc);
+
+	xfer_size = usb_endpoint_maxp(epirq);
+	xfer_buf = devm_kmalloc(&intf->dev, xfer_size, GFP_KERNEL);
+	if (!xfer_buf)
+		return -ENOMEM;
+
+	pxrc->urb = usb_alloc_urb(0, GFP_KERNEL);
+	if (!pxrc->urb)
+		return -ENOMEM;
+
+	error = devm_add_action_or_reset(&intf->dev, pxrc_free_urb, pxrc);
+	if (error)
+		return error;
+
+	usb_fill_int_urb(pxrc->urb, udev,
+			 usb_rcvintpipe(udev, epirq->bEndpointAddress),
+			 xfer_buf, xfer_size, pxrc_usb_irq, pxrc, 1);
+
+	pxrc->input = devm_input_allocate_device(&intf->dev);
+	if (!pxrc->input) {
+		dev_err(&intf->dev, "couldn't allocate input device\n");
+		return -ENOMEM;
+	}
+
+	pxrc->input->name = "PXRC Flight Controller Adapter";
+
+	usb_make_path(udev, pxrc->phys, sizeof(pxrc->phys));
+	strlcat(pxrc->phys, "/input0", sizeof(pxrc->phys));
+	pxrc->input->phys = pxrc->phys;
+
+	usb_to_input_id(udev, &pxrc->input->id);
+
+	pxrc->input->open = pxrc_open;
+	pxrc->input->close = pxrc_close;
+
+	input_set_capability(pxrc->input, EV_KEY, BTN_A);
+	input_set_abs_params(pxrc->input, ABS_X, 0, 255, 0, 0);
+	input_set_abs_params(pxrc->input, ABS_Y, 0, 255, 0, 0);
+	input_set_abs_params(pxrc->input, ABS_RX, 0, 255, 0, 0);
+	input_set_abs_params(pxrc->input, ABS_RY, 0, 255, 0, 0);
+	input_set_abs_params(pxrc->input, ABS_RUDDER, 0, 255, 0, 0);
+	input_set_abs_params(pxrc->input, ABS_THROTTLE, 0, 255, 0, 0);
+	input_set_abs_params(pxrc->input, ABS_MISC, 0, 255, 0, 0);
+
+	input_set_drvdata(pxrc->input, pxrc);
+
+	error = input_register_device(pxrc->input);
+	if (error)
+		return error;
+
+	return 0;
+}
+
+static void pxrc_disconnect(struct usb_interface *intf)
+{
+	/* All driver resources are devm-managed. */
+}
+
+static int pxrc_suspend(struct usb_interface *intf, pm_message_t message)
+{
+	struct pxrc *pxrc = usb_get_intfdata(intf);
+
+	guard(mutex)(&pxrc->pm_mutex);
+	if (pxrc->is_open)
+		usb_kill_urb(pxrc->urb);
+
+	return 0;
+}
+
+static int pxrc_resume(struct usb_interface *intf)
+{
+	struct pxrc *pxrc = usb_get_intfdata(intf);
+
+	guard(mutex)(&pxrc->pm_mutex);
+	if (pxrc->is_open && usb_submit_urb(pxrc->urb, GFP_KERNEL) < 0)
+		return -EIO;
+
+	return 0;
+}
+
+static int pxrc_pre_reset(struct usb_interface *intf)
+{
+	struct pxrc *pxrc = usb_get_intfdata(intf);
+
+	mutex_lock(&pxrc->pm_mutex);
+	usb_kill_urb(pxrc->urb);
+	return 0;
+}
+
+static int pxrc_post_reset(struct usb_interface *intf)
+{
+	struct pxrc *pxrc = usb_get_intfdata(intf);
+	int retval = 0;
+
+	if (pxrc->is_open && usb_submit_urb(pxrc->urb, GFP_KERNEL) < 0)
+		retval = -EIO;
+
+	mutex_unlock(&pxrc->pm_mutex);
+
+	return retval;
+}
+
+static int pxrc_reset_resume(struct usb_interface *intf)
+{
+	return pxrc_resume(intf);
+}
+
+static const struct usb_device_id pxrc_table[] = {
+	{ USB_DEVICE(PXRC_VENDOR_ID, PXRC_PRODUCT_ID) },
+	{ }
+};
+MODULE_DEVICE_TABLE(usb, pxrc_table);
+
+static struct usb_driver pxrc_driver = {
+	.name =		"pxrc",
+	.probe =	pxrc_probe,
+	.disconnect =	pxrc_disconnect,
+	.id_table =	pxrc_table,
+	.suspend	= pxrc_suspend,
+	.resume		= pxrc_resume,
+	.pre_reset	= pxrc_pre_reset,
+	.post_reset	= pxrc_post_reset,
+	.reset_resume	= pxrc_reset_resume,
+};
+
+module_usb_driver(pxrc_driver);
+
+MODULE_AUTHOR("Marcus Folkesson <marcus.folkesson@gmail.com>");
+MODULE_DESCRIPTION("PhoenixRC Flight Controller Adapter");
+MODULE_LICENSE("GPL v2");