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, 100 insertions, 0 deletions

diff --git a/drivers/parisc/eisa_eeprom.c b/drivers/parisc/eisa_eeprom.c
new file mode 100644
index 000000000..2058b4c5b
--- /dev/null
+++ b/drivers/parisc/eisa_eeprom.c
@@ -0,0 +1,100 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/* 
+ *    EISA "eeprom" support routines
+ *
+ *    Copyright (C) 2001 Thomas Bogendoerfer <tsbogend at parisc-linux.org>
+ */
+
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/slab.h>
+#include <linux/fs.h>
+#include <asm/io.h>
+#include <linux/uaccess.h>
+#include <asm/eisa_eeprom.h>
+
+static loff_t eisa_eeprom_llseek(struct file *file, loff_t offset, int origin)
+{
+	return fixed_size_llseek(file, offset, origin, HPEE_MAX_LENGTH);
+}
+
+static ssize_t eisa_eeprom_read(struct file * file,
+			      char __user *buf, size_t count, loff_t *ppos )
+{
+	unsigned char *tmp;
+	ssize_t ret;
+	int i;
+	
+	if (*ppos < 0 || *ppos >= HPEE_MAX_LENGTH)
+		return 0;
+	
+	count = *ppos + count < HPEE_MAX_LENGTH ? count : HPEE_MAX_LENGTH - *ppos;
+	tmp = kmalloc(count, GFP_KERNEL);
+	if (tmp) {
+		for (i = 0; i < count; i++)
+			tmp[i] = readb(eisa_eeprom_addr+(*ppos)++);
+
+		if (copy_to_user (buf, tmp, count))
+			ret = -EFAULT;
+		else
+			ret = count;
+		kfree (tmp);
+	} else
+		ret = -ENOMEM;
+	
+	return ret;
+}
+
+static int eisa_eeprom_open(struct inode *inode, struct file *file)
+{
+	if (file->f_mode & FMODE_WRITE)
+		return -EINVAL;
+   
+	return 0;
+}
+
+static int eisa_eeprom_release(struct inode *inode, struct file *file)
+{
+	return 0;
+}
+
+/*
+ *	The various file operations we support.
+ */
+static const struct file_operations eisa_eeprom_fops = {
+	.owner =	THIS_MODULE,
+	.llseek =	eisa_eeprom_llseek,
+	.read =		eisa_eeprom_read,
+	.open =		eisa_eeprom_open,
+	.release =	eisa_eeprom_release,
+};
+
+static struct miscdevice eisa_eeprom_dev = {
+	EISA_EEPROM_MINOR,
+	"eisa_eeprom",
+	&eisa_eeprom_fops
+};
+
+static int __init eisa_eeprom_init(void)
+{
+	int retval;
+
+	if (!eisa_eeprom_addr)
+		return -ENODEV;
+
+	retval = misc_register(&eisa_eeprom_dev);
+	if (retval < 0) {
+		printk(KERN_ERR "EISA EEPROM: cannot register misc device.\n");
+		return retval;
+	}
+
+	printk(KERN_INFO "EISA EEPROM at 0x%px\n", eisa_eeprom_addr);
+	return 0;
+}
+
+MODULE_DESCRIPTION("EISA eeprom driver");
+MODULE_LICENSE("GPL");
+
+module_init(eisa_eeprom_init);