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, 199 insertions, 0 deletions

diff --git a/fs/sysfs/symlink.c b/fs/sysfs/symlink.c
new file mode 100644
index 000000000..5f9c05fb1
--- /dev/null
+++ b/fs/sysfs/symlink.c
@@ -0,0 +1,199 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * fs/sysfs/symlink.c - sysfs symlink implementation
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ *
+ * Please see Documentation/filesystems/sysfs.rst for more information.
+ */
+
+#include <linux/fs.h>
+#include <linux/module.h>
+#include <linux/kobject.h>
+#include <linux/mutex.h>
+#include <linux/security.h>
+
+#include "sysfs.h"
+
+static int sysfs_do_create_link_sd(struct kernfs_node *parent,
+				   struct kobject *target_kobj,
+				   const char *name, int warn)
+{
+	struct kernfs_node *kn, *target = NULL;
+
+	if (WARN_ON(!name || !parent))
+		return -EINVAL;
+
+	/*
+	 * We don't own @target_kobj and it may be removed at any time.
+	 * Synchronize using sysfs_symlink_target_lock.  See
+	 * sysfs_remove_dir() for details.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	if (target_kobj->sd) {
+		target = target_kobj->sd;
+		kernfs_get(target);
+	}
+	spin_unlock(&sysfs_symlink_target_lock);
+
+	if (!target)
+		return -ENOENT;
+
+	kn = kernfs_create_link(parent, name, target);
+	kernfs_put(target);
+
+	if (!IS_ERR(kn))
+		return 0;
+
+	if (warn && PTR_ERR(kn) == -EEXIST)
+		sysfs_warn_dup(parent, name);
+	return PTR_ERR(kn);
+}
+
+/**
+ *	sysfs_create_link_sd - create symlink to a given object.
+ *	@kn:		directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ */
+int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
+			 const char *name)
+{
+	return sysfs_do_create_link_sd(kn, target, name, 1);
+}
+
+static int sysfs_do_create_link(struct kobject *kobj, struct kobject *target,
+				const char *name, int warn)
+{
+	struct kernfs_node *parent = NULL;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	if (!parent)
+		return -EFAULT;
+
+	return sysfs_do_create_link_sd(parent, target, name, warn);
+}
+
+/**
+ *	sysfs_create_link - create symlink between two objects.
+ *	@kobj:	object whose directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ */
+int sysfs_create_link(struct kobject *kobj, struct kobject *target,
+		      const char *name)
+{
+	return sysfs_do_create_link(kobj, target, name, 1);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_link);
+
+/**
+ *	sysfs_create_link_nowarn - create symlink between two objects.
+ *	@kobj:	object whose directory we're creating the link in.
+ *	@target:	object we're pointing to.
+ *	@name:		name of the symlink.
+ *
+ *	This function does the same as sysfs_create_link(), but it
+ *	doesn't warn if the link already exists.
+ */
+int sysfs_create_link_nowarn(struct kobject *kobj, struct kobject *target,
+			     const char *name)
+{
+	return sysfs_do_create_link(kobj, target, name, 0);
+}
+EXPORT_SYMBOL_GPL(sysfs_create_link_nowarn);
+
+/**
+ *	sysfs_delete_link - remove symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@targ:	object we're pointing to.
+ *	@name:	name of the symlink to remove.
+ *
+ *	Unlike sysfs_remove_link sysfs_delete_link has enough information
+ *	to successfully delete symlinks in tagged directories.
+ */
+void sysfs_delete_link(struct kobject *kobj, struct kobject *targ,
+			const char *name)
+{
+	const struct ns_common *ns = NULL;
+
+	/*
+	 * We don't own @target and it may be removed at any time.
+	 * Synchronize using sysfs_symlink_target_lock.  See
+	 * sysfs_remove_dir() for details.
+	 */
+	spin_lock(&sysfs_symlink_target_lock);
+	if (targ->sd && kernfs_ns_enabled(kobj->sd))
+		ns = targ->sd->ns;
+	spin_unlock(&sysfs_symlink_target_lock);
+	kernfs_remove_by_name_ns(kobj->sd, name, ns);
+}
+
+/**
+ *	sysfs_remove_link - remove symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@name:	name of the symlink to remove.
+ */
+void sysfs_remove_link(struct kobject *kobj, const char *name)
+{
+	struct kernfs_node *parent = NULL;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	kernfs_remove_by_name(parent, name);
+}
+EXPORT_SYMBOL_GPL(sysfs_remove_link);
+
+/**
+ *	sysfs_rename_link_ns - rename symlink in object's directory.
+ *	@kobj:	object we're acting for.
+ *	@targ:	object we're pointing to.
+ *	@old:	previous name of the symlink.
+ *	@new:	new name of the symlink.
+ *	@new_ns: new namespace of the symlink.
+ *
+ *	A helper function for the common rename symlink idiom.
+ */
+int sysfs_rename_link_ns(struct kobject *kobj, struct kobject *targ,
+			 const char *old, const char *new,
+			 const struct ns_common *new_ns)
+{
+	struct kernfs_node *parent, *kn = NULL;
+	const struct ns_common *old_ns = NULL;
+	int result;
+
+	if (!kobj)
+		parent = sysfs_root_kn;
+	else
+		parent = kobj->sd;
+
+	if (targ->sd)
+		old_ns = targ->sd->ns;
+
+	result = -ENOENT;
+	kn = kernfs_find_and_get_ns(parent, old, old_ns);
+	if (!kn)
+		goto out;
+
+	result = -EINVAL;
+	if (kernfs_type(kn) != KERNFS_LINK)
+		goto out;
+	if (kn->symlink.target_kn->priv != targ)
+		goto out;
+
+	result = kernfs_rename_ns(kn, parent, new, new_ns);
+
+out:
+	kernfs_put(kn);
+	return result;
+}
+EXPORT_SYMBOL_GPL(sysfs_rename_link_ns);