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, 355 insertions, 0 deletions

diff --git a/drivers/usb/misc/cytherm.c b/drivers/usb/misc/cytherm.c
new file mode 100644
index 000000000..b183df982
--- /dev/null
+++ b/drivers/usb/misc/cytherm.c
@@ -0,0 +1,355 @@
+// SPDX-License-Identifier: GPL-2.0
+/* -*- linux-c -*-
+ * Cypress USB Thermometer driver 
+ * 
+ * Copyright (c) 2004 Erik Rigtorp <erkki@linux.nu> <erik@rigtorp.com>
+ * 
+ * This driver works with Elektor magazine USB Interface as published in 
+ * issue #291. It should also work with the original starter kit/demo board
+ * from Cypress.
+ */
+
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/module.h>
+#include <linux/usb.h>
+
+#define DRIVER_AUTHOR "Erik Rigtorp"
+#define DRIVER_DESC "Cypress USB Thermometer driver"
+
+#define USB_SKEL_VENDOR_ID	0x04b4
+#define USB_SKEL_PRODUCT_ID	0x0002
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
+	{ }
+};
+MODULE_DEVICE_TABLE (usb, id_table);
+
+/* Structure to hold all of our device specific stuff */
+struct usb_cytherm {
+	struct usb_device    *udev;	 /* save off the usb device pointer */
+	struct usb_interface *interface; /* the interface for this device */
+	int brightness;
+};
+
+
+/* Vendor requests */
+/* They all operate on one byte at a time */
+#define PING       0x00
+#define READ_ROM   0x01 /* Reads form ROM, value = address */
+#define READ_RAM   0x02 /* Reads form RAM, value = address */
+#define WRITE_RAM  0x03 /* Write to RAM, value = address, index = data */
+#define READ_PORT  0x04 /* Reads from port, value = address */
+#define WRITE_PORT 0x05 /* Write to port, value = address, index = data */ 
+
+
+/* Send a vendor command to device */
+static int vendor_command(struct usb_device *dev, unsigned char request, 
+			  unsigned char value, unsigned char index,
+			  void *buf, int size)
+{
+	return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
+			       request, 
+			       USB_DIR_IN | USB_TYPE_VENDOR | USB_RECIP_OTHER,
+			       value, 
+			       index, buf, size,
+			       USB_CTRL_GET_TIMEOUT);
+}
+
+
+
+#define BRIGHTNESS 0x2c     /* RAM location for brightness value */
+#define BRIGHTNESS_SEM 0x2b /* RAM location for brightness semaphore */
+
+static ssize_t brightness_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);    
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);     
+
+	return sprintf(buf, "%i", cytherm->brightness);
+}
+
+static ssize_t brightness_store(struct device *dev, struct device_attribute *attr, const char *buf,
+			      size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	unsigned char *buffer;
+	int retval;
+   
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	cytherm->brightness = simple_strtoul(buf, NULL, 10);
+   
+	if (cytherm->brightness > 0xFF)
+		cytherm->brightness = 0xFF;
+	else if (cytherm->brightness < 0)
+		cytherm->brightness = 0;
+   
+	/* Set brightness */
+	retval = vendor_command(cytherm->udev, WRITE_RAM, BRIGHTNESS, 
+				cytherm->brightness, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+	/* Inform µC that we have changed the brightness setting */
+	retval = vendor_command(cytherm->udev, WRITE_RAM, BRIGHTNESS_SEM,
+				0x01, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+   
+	kfree(buffer);
+   
+	return count;
+}
+static DEVICE_ATTR_RW(brightness);
+
+
+#define TEMP 0x33 /* RAM location for temperature */
+#define SIGN 0x34 /* RAM location for temperature sign */
+
+static ssize_t temp_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	int retval;
+	unsigned char *buffer;
+
+	int temp, sign;
+   
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	/* read temperature */
+	retval = vendor_command(cytherm->udev, READ_RAM, TEMP, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+	temp = buffer[1];
+   
+	/* read sign */
+	retval = vendor_command(cytherm->udev, READ_RAM, SIGN, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+	sign = buffer[1];
+
+	kfree(buffer);
+   
+	return sprintf(buf, "%c%i.%i", sign ? '-' : '+', temp >> 1,
+		       5*(temp - ((temp >> 1) << 1)));
+}
+static DEVICE_ATTR_RO(temp);
+
+
+#define BUTTON 0x7a
+
+static ssize_t button_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	int retval;
+	unsigned char *buffer;
+
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	/* check button */
+	retval = vendor_command(cytherm->udev, READ_RAM, BUTTON, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+   
+	retval = buffer[1];
+
+	kfree(buffer);
+
+	if (retval)
+		return sprintf(buf, "1");
+	else
+		return sprintf(buf, "0");
+}
+static DEVICE_ATTR_RO(button);
+
+
+static ssize_t port0_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	int retval;
+	unsigned char *buffer;
+
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	retval = vendor_command(cytherm->udev, READ_PORT, 0, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+
+	retval = buffer[1];
+
+	kfree(buffer);
+
+	return sprintf(buf, "%d", retval);
+}
+
+
+static ssize_t port0_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	unsigned char *buffer;
+	int retval;
+	int tmp;
+   
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	tmp = simple_strtoul(buf, NULL, 10);
+   
+	if (tmp > 0xFF)
+		tmp = 0xFF;
+	else if (tmp < 0)
+		tmp = 0;
+   
+	retval = vendor_command(cytherm->udev, WRITE_PORT, 0,
+				tmp, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+
+	kfree(buffer);
+
+	return count;
+}
+static DEVICE_ATTR_RW(port0);
+
+static ssize_t port1_show(struct device *dev, struct device_attribute *attr, char *buf)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	int retval;
+	unsigned char *buffer;
+
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	retval = vendor_command(cytherm->udev, READ_PORT, 1, 0, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+   
+	retval = buffer[1];
+
+	kfree(buffer);
+
+	return sprintf(buf, "%d", retval);
+}
+
+
+static ssize_t port1_store(struct device *dev, struct device_attribute *attr, const char *buf, size_t count)
+{
+	struct usb_interface *intf = to_usb_interface(dev);
+	struct usb_cytherm *cytherm = usb_get_intfdata(intf);
+
+	unsigned char *buffer;
+	int retval;
+	int tmp;
+   
+	buffer = kmalloc(8, GFP_KERNEL);
+	if (!buffer)
+		return 0;
+
+	tmp = simple_strtoul(buf, NULL, 10);
+   
+	if (tmp > 0xFF)
+		tmp = 0xFF;
+	else if (tmp < 0)
+		tmp = 0;
+   
+	retval = vendor_command(cytherm->udev, WRITE_PORT, 1,
+				tmp, buffer, 8);
+	if (retval)
+		dev_dbg(&cytherm->udev->dev, "retval = %d\n", retval);
+
+	kfree(buffer);
+
+	return count;
+}
+static DEVICE_ATTR_RW(port1);
+
+static struct attribute *cytherm_attrs[] = {
+	&dev_attr_brightness.attr,
+	&dev_attr_temp.attr,
+	&dev_attr_button.attr,
+	&dev_attr_port0.attr,
+	&dev_attr_port1.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(cytherm);
+
+static int cytherm_probe(struct usb_interface *interface, 
+			 const struct usb_device_id *id)
+{
+	struct usb_device *udev = interface_to_usbdev(interface);
+	struct usb_cytherm *dev;
+	int retval = -ENOMEM;
+
+	dev = kzalloc_obj(struct usb_cytherm);
+	if (!dev)
+		goto error_mem;
+
+	dev->udev = udev;
+
+	usb_set_intfdata(interface, dev);
+
+	dev->brightness = 0xFF;
+
+	dev_info(&interface->dev,
+		  "Cypress thermometer device now attached\n");
+	return 0;
+
+error_mem:
+	return retval;
+}
+
+static void cytherm_disconnect(struct usb_interface *interface)
+{
+	struct usb_cytherm *dev;
+
+	dev = usb_get_intfdata(interface);
+
+	/* first remove the files, then NULL the pointer */
+	usb_set_intfdata(interface, NULL);
+
+	kfree(dev);
+
+	dev_info(&interface->dev, "Cypress thermometer now disconnected\n");
+}
+
+/* usb specific object needed to register this driver with the usb subsystem */
+static struct usb_driver cytherm_driver = {
+	.name =		"cytherm",
+	.probe =	cytherm_probe,
+	.disconnect =	cytherm_disconnect,
+	.id_table =	id_table,
+	.dev_groups =	cytherm_groups,
+};
+
+module_usb_driver(cytherm_driver);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL");