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, 158 insertions, 0 deletions

diff --git a/net/atm/atm_sysfs.c b/net/atm/atm_sysfs.c
new file mode 100644
index 000000000..0676a9c33
--- /dev/null
+++ b/net/atm/atm_sysfs.c
@@ -0,0 +1,158 @@
+// SPDX-License-Identifier: GPL-2.0
+/* ATM driver model support. */
+
+#include <linux/kernel.h>
+#include <linux/slab.h>
+#include <linux/init.h>
+#include <linux/kobject.h>
+#include <linux/atmdev.h>
+#include "common.h"
+#include "resources.h"
+
+#define to_atm_dev(cldev) container_of(cldev, struct atm_dev, class_dev)
+
+static ssize_t type_show(struct device *cdev,
+			 struct device_attribute *attr, char *buf)
+{
+	struct atm_dev *adev = to_atm_dev(cdev);
+
+	return scnprintf(buf, PAGE_SIZE, "%s\n", adev->type);
+}
+
+static ssize_t address_show(struct device *cdev,
+			    struct device_attribute *attr, char *buf)
+{
+	struct atm_dev *adev = to_atm_dev(cdev);
+
+	return scnprintf(buf, PAGE_SIZE, "%pM\n", adev->esi);
+}
+
+static ssize_t atmindex_show(struct device *cdev,
+			     struct device_attribute *attr, char *buf)
+{
+	struct atm_dev *adev = to_atm_dev(cdev);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n", adev->number);
+}
+
+static ssize_t carrier_show(struct device *cdev,
+			    struct device_attribute *attr, char *buf)
+{
+	struct atm_dev *adev = to_atm_dev(cdev);
+
+	return scnprintf(buf, PAGE_SIZE, "%d\n",
+			 adev->signal == ATM_PHY_SIG_LOST ? 0 : 1);
+}
+
+static ssize_t link_rate_show(struct device *cdev,
+			      struct device_attribute *attr, char *buf)
+{
+	struct atm_dev *adev = to_atm_dev(cdev);
+	int link_rate;
+
+	/* show the link rate, not the data rate */
+	switch (adev->link_rate) {
+	case ATM_OC3_PCR:
+		link_rate = 155520000;
+		break;
+	case ATM_OC12_PCR:
+		link_rate = 622080000;
+		break;
+	case ATM_25_PCR:
+		link_rate = 25600000;
+		break;
+	default:
+		link_rate = adev->link_rate * 8 * 53;
+	}
+	return scnprintf(buf, PAGE_SIZE, "%d\n", link_rate);
+}
+
+static DEVICE_ATTR_RO(address);
+static DEVICE_ATTR_RO(atmindex);
+static DEVICE_ATTR_RO(carrier);
+static DEVICE_ATTR_RO(type);
+static DEVICE_ATTR_RO(link_rate);
+
+static struct device_attribute *atm_attrs[] = {
+	&dev_attr_address,
+	&dev_attr_atmindex,
+	&dev_attr_carrier,
+	&dev_attr_type,
+	&dev_attr_link_rate,
+	NULL
+};
+
+
+static int atm_uevent(const struct device *cdev, struct kobj_uevent_env *env)
+{
+	const struct atm_dev *adev;
+
+	if (!cdev)
+		return -ENODEV;
+
+	adev = to_atm_dev(cdev);
+
+	if (add_uevent_var(env, "NAME=%s%d", adev->type, adev->number))
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void atm_release(struct device *cdev)
+{
+	struct atm_dev *adev = to_atm_dev(cdev);
+
+	kfree(adev);
+}
+
+static struct class atm_class = {
+	.name		= "atm",
+	.dev_release	= atm_release,
+	.dev_uevent		= atm_uevent,
+};
+
+int atm_register_sysfs(struct atm_dev *adev, struct device *parent)
+{
+	struct device *cdev = &adev->class_dev;
+	int i, j, err;
+
+	cdev->class = &atm_class;
+	cdev->parent = parent;
+	dev_set_drvdata(cdev, adev);
+
+	dev_set_name(cdev, "%s%d", adev->type, adev->number);
+	err = device_register(cdev);
+	if (err < 0)
+		return err;
+
+	for (i = 0; atm_attrs[i]; i++) {
+		err = device_create_file(cdev, atm_attrs[i]);
+		if (err)
+			goto err_out;
+	}
+
+	return 0;
+
+err_out:
+	for (j = 0; j < i; j++)
+		device_remove_file(cdev, atm_attrs[j]);
+	device_del(cdev);
+	return err;
+}
+
+void atm_unregister_sysfs(struct atm_dev *adev)
+{
+	struct device *cdev = &adev->class_dev;
+
+	device_del(cdev);
+}
+
+int __init atm_sysfs_init(void)
+{
+	return class_register(&atm_class);
+}
+
+void __exit atm_sysfs_exit(void)
+{
+	class_unregister(&atm_class);
+}