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, 86 insertions, 0 deletions

diff --git a/drivers/pnp/isapnp/proc.c b/drivers/pnp/isapnp/proc.c
new file mode 100644
index 000000000..55ae72a28
--- /dev/null
+++ b/drivers/pnp/isapnp/proc.c
@@ -0,0 +1,86 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  ISA Plug & Play support
+ *  Copyright (c) by Jaroslav Kysela <perex@perex.cz>
+ */
+
+#include <linux/module.h>
+#include <linux/isapnp.h>
+#include <linux/proc_fs.h>
+#include <linux/init.h>
+#include <linux/uaccess.h>
+
+extern struct pnp_protocol isapnp_protocol;
+
+static struct proc_dir_entry *isapnp_proc_bus_dir = NULL;
+
+static loff_t isapnp_proc_bus_lseek(struct file *file, loff_t off, int whence)
+{
+	return fixed_size_llseek(file, off, whence, 256);
+}
+
+static ssize_t isapnp_proc_bus_read(struct file *file, char __user * buf,
+				    size_t nbytes, loff_t * ppos)
+{
+	struct pnp_dev *dev = pde_data(file_inode(file));
+	int pos = *ppos;
+	int cnt, size = 256;
+
+	if (pos >= size)
+		return 0;
+	if (nbytes >= size)
+		nbytes = size;
+	if (pos + nbytes > size)
+		nbytes = size - pos;
+	cnt = nbytes;
+
+	if (!access_ok(buf, cnt))
+		return -EINVAL;
+
+	isapnp_cfg_begin(dev->card->number, dev->number);
+	for (; pos < 256 && cnt > 0; pos++, buf++, cnt--) {
+		unsigned char val;
+		val = isapnp_read_byte(pos);
+		__put_user(val, buf);
+	}
+	isapnp_cfg_end();
+
+	*ppos = pos;
+	return nbytes;
+}
+
+static const struct proc_ops isapnp_proc_bus_proc_ops = {
+	.proc_lseek	= isapnp_proc_bus_lseek,
+	.proc_read	= isapnp_proc_bus_read,
+};
+
+static int isapnp_proc_attach_device(struct pnp_dev *dev)
+{
+	struct pnp_card *bus = dev->card;
+	char name[16];
+
+	if (!bus->procdir) {
+		sprintf(name, "%02x", bus->number);
+		bus->procdir = proc_mkdir(name, isapnp_proc_bus_dir);
+		if (!bus->procdir)
+			return -ENOMEM;
+	}
+	sprintf(name, "%02x", dev->number);
+	dev->procent = proc_create_data(name, S_IFREG | S_IRUGO, bus->procdir,
+					    &isapnp_proc_bus_proc_ops, dev);
+	if (!dev->procent)
+		return -ENOMEM;
+	proc_set_size(dev->procent, 256);
+	return 0;
+}
+
+int __init isapnp_proc_init(void)
+{
+	struct pnp_dev *dev;
+
+	isapnp_proc_bus_dir = proc_mkdir("bus/isapnp", NULL);
+	protocol_for_each_dev(&isapnp_protocol, dev) {
+		isapnp_proc_attach_device(dev);
+	}
+	return 0;
+}