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, 204 insertions, 0 deletions

diff --git a/drivers/input/tablet/kbtab.c b/drivers/input/tablet/kbtab.c
new file mode 100644
index 000000000..6ce70c8e2
--- /dev/null
+++ b/drivers/input/tablet/kbtab.c
@@ -0,0 +1,204 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/usb/input.h>
+#include <linux/unaligned.h>
+
+/*
+ * Pressure-threshold modules param code from Alex Perry <alex.perry@ieee.org>
+ */
+
+MODULE_AUTHOR("Josh Myer <josh@joshisanerd.com>");
+MODULE_DESCRIPTION("USB KB Gear JamStudio Tablet driver");
+MODULE_LICENSE("GPL");
+
+#define USB_VENDOR_ID_KBGEAR	0x084e
+
+static int kb_pressure_click = 0x10;
+module_param(kb_pressure_click, int, 0);
+MODULE_PARM_DESC(kb_pressure_click, "pressure threshold for clicks");
+
+struct kbtab {
+	unsigned char *data;
+	dma_addr_t data_dma;
+	struct input_dev *dev;
+	struct usb_interface *intf;
+	struct urb *irq;
+	char phys[32];
+};
+
+static void kbtab_irq(struct urb *urb)
+{
+	struct kbtab *kbtab = urb->context;
+	unsigned char *data = kbtab->data;
+	struct input_dev *dev = kbtab->dev;
+	int pressure;
+	int retval;
+
+	switch (urb->status) {
+	case 0:
+		/* success */
+		break;
+	case -ECONNRESET:
+	case -ENOENT:
+	case -ESHUTDOWN:
+		/* this urb is terminated, clean up */
+		dev_dbg(&kbtab->intf->dev,
+			"%s - urb shutting down with status: %d\n",
+			__func__, urb->status);
+		return;
+	default:
+		dev_dbg(&kbtab->intf->dev,
+			"%s - nonzero urb status received: %d\n",
+			__func__, urb->status);
+		goto exit;
+	}
+
+
+	input_report_key(dev, BTN_TOOL_PEN, 1);
+
+	input_report_abs(dev, ABS_X, get_unaligned_le16(&data[1]));
+	input_report_abs(dev, ABS_Y, get_unaligned_le16(&data[3]));
+
+	/*input_report_key(dev, BTN_TOUCH , data[0] & 0x01);*/
+	input_report_key(dev, BTN_RIGHT, data[0] & 0x02);
+
+	pressure = data[5];
+	if (kb_pressure_click == -1)
+		input_report_abs(dev, ABS_PRESSURE, pressure);
+	else
+		input_report_key(dev, BTN_LEFT, pressure > kb_pressure_click ? 1 : 0);
+
+	input_sync(dev);
+
+ exit:
+	retval = usb_submit_urb(urb, GFP_ATOMIC);
+	if (retval)
+		dev_err(&kbtab->intf->dev,
+			"%s - usb_submit_urb failed with result %d\n",
+			__func__, retval);
+}
+
+static const struct usb_device_id kbtab_ids[] = {
+	{ USB_DEVICE(USB_VENDOR_ID_KBGEAR, 0x1001), .driver_info = 0 },
+	{ }
+};
+
+MODULE_DEVICE_TABLE(usb, kbtab_ids);
+
+static int kbtab_open(struct input_dev *dev)
+{
+	struct kbtab *kbtab = input_get_drvdata(dev);
+	struct usb_device *udev = interface_to_usbdev(kbtab->intf);
+
+	kbtab->irq->dev = udev;
+	if (usb_submit_urb(kbtab->irq, GFP_KERNEL))
+		return -EIO;
+
+	return 0;
+}
+
+static void kbtab_close(struct input_dev *dev)
+{
+	struct kbtab *kbtab = input_get_drvdata(dev);
+
+	usb_kill_urb(kbtab->irq);
+}
+
+static int kbtab_probe(struct usb_interface *intf, const struct usb_device_id *id)
+{
+	struct usb_device *dev = interface_to_usbdev(intf);
+	struct usb_endpoint_descriptor *endpoint;
+	struct kbtab *kbtab;
+	struct input_dev *input_dev;
+	int error = -ENOMEM;
+
+	if (intf->cur_altsetting->desc.bNumEndpoints < 1)
+		return -ENODEV;
+
+	endpoint = &intf->cur_altsetting->endpoint[0].desc;
+	if (!usb_endpoint_is_int_in(endpoint))
+		return -ENODEV;
+
+	kbtab = kzalloc_obj(*kbtab);
+	input_dev = input_allocate_device();
+	if (!kbtab || !input_dev)
+		goto fail1;
+
+	kbtab->data = usb_alloc_coherent(dev, 8, GFP_KERNEL, &kbtab->data_dma);
+	if (!kbtab->data)
+		goto fail1;
+
+	kbtab->irq = usb_alloc_urb(0, GFP_KERNEL);
+	if (!kbtab->irq)
+		goto fail2;
+
+	kbtab->intf = intf;
+	kbtab->dev = input_dev;
+
+	usb_make_path(dev, kbtab->phys, sizeof(kbtab->phys));
+	strlcat(kbtab->phys, "/input0", sizeof(kbtab->phys));
+
+	input_dev->name = "KB Gear Tablet";
+	input_dev->phys = kbtab->phys;
+	usb_to_input_id(dev, &input_dev->id);
+	input_dev->dev.parent = &intf->dev;
+
+	input_set_drvdata(input_dev, kbtab);
+
+	input_dev->open = kbtab_open;
+	input_dev->close = kbtab_close;
+
+	input_dev->evbit[0] |= BIT_MASK(EV_KEY) | BIT_MASK(EV_ABS);
+	input_dev->keybit[BIT_WORD(BTN_LEFT)] |=
+		BIT_MASK(BTN_LEFT) | BIT_MASK(BTN_RIGHT);
+	input_dev->keybit[BIT_WORD(BTN_DIGI)] |=
+		BIT_MASK(BTN_TOOL_PEN) | BIT_MASK(BTN_TOUCH);
+	input_set_abs_params(input_dev, ABS_X, 0, 0x2000, 4, 0);
+	input_set_abs_params(input_dev, ABS_Y, 0, 0x1750, 4, 0);
+	input_set_abs_params(input_dev, ABS_PRESSURE, 0, 0xff, 0, 0);
+
+	usb_fill_int_urb(kbtab->irq, dev,
+			 usb_rcvintpipe(dev, endpoint->bEndpointAddress),
+			 kbtab->data, 8,
+			 kbtab_irq, kbtab, endpoint->bInterval);
+	kbtab->irq->transfer_dma = kbtab->data_dma;
+	kbtab->irq->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
+
+	error = input_register_device(kbtab->dev);
+	if (error)
+		goto fail3;
+
+	usb_set_intfdata(intf, kbtab);
+
+	return 0;
+
+ fail3:	usb_free_urb(kbtab->irq);
+ fail2:	usb_free_coherent(dev, 8, kbtab->data, kbtab->data_dma);
+ fail1:	input_free_device(input_dev);
+	kfree(kbtab);
+	return error;
+}
+
+static void kbtab_disconnect(struct usb_interface *intf)
+{
+	struct kbtab *kbtab = usb_get_intfdata(intf);
+	struct usb_device *udev = interface_to_usbdev(intf);
+
+	usb_set_intfdata(intf, NULL);
+
+	input_unregister_device(kbtab->dev);
+	usb_free_urb(kbtab->irq);
+	usb_free_coherent(udev, 8, kbtab->data, kbtab->data_dma);
+	kfree(kbtab);
+}
+
+static struct usb_driver kbtab_driver = {
+	.name =		"kbtab",
+	.probe =	kbtab_probe,
+	.disconnect =	kbtab_disconnect,
+	.id_table =	kbtab_ids,
+};
+
+module_usb_driver(kbtab_driver);