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, 190 insertions, 0 deletions

diff --git a/fs/configfs/item.c b/fs/configfs/item.c
new file mode 100644
index 000000000..c378b5cbf
--- /dev/null
+++ b/fs/configfs/item.c
@@ -0,0 +1,190 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * item.c - library routines for handling generic config items
+ *
+ * Based on kobject:
+ *	kobject is Copyright (c) 2002-2003 Patrick Mochel
+ *
+ * configfs Copyright (C) 2005 Oracle.  All rights reserved.
+ *
+ * Please see the file Documentation/filesystems/configfs.rst for
+ * critical information about using the config_item interface.
+ */
+
+#include <linux/string.h>
+#include <linux/module.h>
+#include <linux/stat.h>
+#include <linux/slab.h>
+
+#include <linux/configfs.h>
+
+
+static inline struct config_item *to_item(struct list_head *entry)
+{
+	return container_of(entry, struct config_item, ci_entry);
+}
+
+/* Evil kernel */
+static void config_item_release(struct kref *kref);
+
+/**
+ *	config_item_init - initialize item.
+ *	@item:	item in question.
+ */
+static void config_item_init(struct config_item *item)
+{
+	kref_init(&item->ci_kref);
+	INIT_LIST_HEAD(&item->ci_entry);
+}
+
+/**
+ *	config_item_set_name - Set the name of an item
+ *	@item:	item.
+ *	@fmt:  The vsnprintf()'s format string.
+ *
+ *	If strlen(name) >= CONFIGFS_ITEM_NAME_LEN, then use a
+ *	dynamically allocated string that @item->ci_name points to.
+ *	Otherwise, use the static @item->ci_namebuf array.
+ */
+int config_item_set_name(struct config_item *item, const char *fmt, ...)
+{
+	int limit = CONFIGFS_ITEM_NAME_LEN;
+	int need;
+	va_list args;
+	char *name;
+
+	/*
+	 * First, try the static array
+	 */
+	va_start(args, fmt);
+	need = vsnprintf(item->ci_namebuf, limit, fmt, args);
+	va_end(args);
+	if (need < limit)
+		name = item->ci_namebuf;
+	else {
+		va_start(args, fmt);
+		name = kvasprintf(GFP_KERNEL, fmt, args);
+		va_end(args);
+		if (!name)
+			return -ENOMEM;
+	}
+
+	/* Free the old name, if necessary. */
+	if (item->ci_name && item->ci_name != item->ci_namebuf)
+		kfree(item->ci_name);
+
+	/* Now, set the new name */
+	item->ci_name = name;
+	return 0;
+}
+EXPORT_SYMBOL(config_item_set_name);
+
+void config_item_init_type_name(struct config_item *item,
+				const char *name,
+				const struct config_item_type *type)
+{
+	config_item_set_name(item, "%s", name);
+	item->ci_type = type;
+	config_item_init(item);
+}
+EXPORT_SYMBOL(config_item_init_type_name);
+
+void config_group_init_type_name(struct config_group *group, const char *name,
+			 const struct config_item_type *type)
+{
+	config_item_set_name(&group->cg_item, "%s", name);
+	group->cg_item.ci_type = type;
+	config_group_init(group);
+}
+EXPORT_SYMBOL(config_group_init_type_name);
+
+struct config_item *config_item_get(struct config_item *item)
+{
+	if (item)
+		kref_get(&item->ci_kref);
+	return item;
+}
+EXPORT_SYMBOL(config_item_get);
+
+struct config_item *config_item_get_unless_zero(struct config_item *item)
+{
+	if (item && kref_get_unless_zero(&item->ci_kref))
+		return item;
+	return NULL;
+}
+EXPORT_SYMBOL(config_item_get_unless_zero);
+
+static void config_item_cleanup(struct config_item *item)
+{
+	const struct config_item_type *t = item->ci_type;
+	struct config_group *s = item->ci_group;
+	struct config_item *parent = item->ci_parent;
+
+	pr_debug("config_item %s: cleaning up\n", config_item_name(item));
+	if (item->ci_name != item->ci_namebuf)
+		kfree(item->ci_name);
+	item->ci_name = NULL;
+	if (t && t->ct_item_ops && t->ct_item_ops->release)
+		t->ct_item_ops->release(item);
+	if (s)
+		config_group_put(s);
+	if (parent)
+		config_item_put(parent);
+}
+
+static void config_item_release(struct kref *kref)
+{
+	config_item_cleanup(container_of(kref, struct config_item, ci_kref));
+}
+
+/**
+ *	config_item_put - decrement refcount for item.
+ *	@item:	item.
+ *
+ *	Decrement the refcount, and if 0, call config_item_cleanup().
+ */
+void config_item_put(struct config_item *item)
+{
+	if (item)
+		kref_put(&item->ci_kref, config_item_release);
+}
+EXPORT_SYMBOL(config_item_put);
+
+/**
+ *	config_group_init - initialize a group for use
+ *	@group:	config_group
+ */
+void config_group_init(struct config_group *group)
+{
+	config_item_init(&group->cg_item);
+	INIT_LIST_HEAD(&group->cg_children);
+	INIT_LIST_HEAD(&group->default_groups);
+}
+EXPORT_SYMBOL(config_group_init);
+
+/**
+ *	config_group_find_item - search for item in group.
+ *	@group:	group we're looking in.
+ *	@name:	item's name.
+ *
+ *	Iterate over @group->cg_list, looking for a matching config_item.
+ *	If matching item is found take a reference and return the item.
+ *	Caller must have locked group via @group->cg_subsys->su_mtx.
+ */
+struct config_item *config_group_find_item(struct config_group *group,
+					   const char *name)
+{
+	struct list_head *entry;
+	struct config_item *ret = NULL;
+
+	list_for_each(entry, &group->cg_children) {
+		struct config_item *item = to_item(entry);
+		if (config_item_name(item) &&
+		    !strcmp(config_item_name(item), name)) {
+			ret = config_item_get(item);
+			break;
+		}
+	}
+	return ret;
+}
+EXPORT_SYMBOL(config_group_find_item);