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, 43 insertions, 0 deletions

diff --git a/fs/sysfs/sysfs.h b/fs/sysfs/sysfs.h
new file mode 100644
index 000000000..f4583dcaf
--- /dev/null
+++ b/fs/sysfs/sysfs.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * fs/sysfs/sysfs.h - sysfs internal header file
+ *
+ * Copyright (c) 2001-3 Patrick Mochel
+ * Copyright (c) 2007 SUSE Linux Products GmbH
+ * Copyright (c) 2007 Tejun Heo <teheo@suse.de>
+ */
+
+#ifndef __SYSFS_INTERNAL_H
+#define __SYSFS_INTERNAL_H
+
+#include <linux/sysfs.h>
+
+/*
+ * mount.c
+ */
+extern struct kernfs_node *sysfs_root_kn;
+
+/*
+ * dir.c
+ */
+extern spinlock_t sysfs_symlink_target_lock;
+
+void sysfs_warn_dup(struct kernfs_node *parent, const char *name);
+
+/*
+ * file.c
+ */
+int sysfs_add_file_mode_ns(struct kernfs_node *parent,
+		const struct attribute *attr, umode_t amode, kuid_t uid,
+		kgid_t gid, const struct ns_common *ns);
+int sysfs_add_bin_file_mode_ns(struct kernfs_node *parent,
+		const struct bin_attribute *battr, umode_t mode, size_t size,
+		kuid_t uid, kgid_t gid, const struct ns_common *ns);
+
+/*
+ * symlink.c
+ */
+int sysfs_create_link_sd(struct kernfs_node *kn, struct kobject *target,
+			 const char *name);
+
+#endif	/* __SYSFS_INTERNAL_H */