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, 34 insertions, 0 deletions

diff --git a/drivers/leds/leds.h b/drivers/leds/leds.h
new file mode 100644
index 000000000..bee46651e
--- /dev/null
+++ b/drivers/leds/leds.h
@@ -0,0 +1,34 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+/*
+ * LED Core
+ *
+ * Copyright 2005 Openedhand Ltd.
+ *
+ * Author: Richard Purdie <rpurdie@openedhand.com>
+ */
+#ifndef __LEDS_H_INCLUDED
+#define __LEDS_H_INCLUDED
+
+#include <linux/rwsem.h>
+#include <linux/leds.h>
+
+static inline int led_get_brightness(struct led_classdev *led_cdev)
+{
+	return led_cdev->brightness;
+}
+
+void led_init_core(struct led_classdev *led_cdev);
+void led_stop_software_blink(struct led_classdev *led_cdev);
+void led_set_brightness_nopm(struct led_classdev *led_cdev, unsigned int value);
+void led_set_brightness_nosleep(struct led_classdev *led_cdev, unsigned int value);
+ssize_t led_trigger_read(struct file *filp, struct kobject *kobj,
+			const struct bin_attribute *attr, char *buf,
+			loff_t pos, size_t count);
+ssize_t led_trigger_write(struct file *filp, struct kobject *kobj,
+			const struct bin_attribute *bin_attr, char *buf,
+			loff_t pos, size_t count);
+
+extern struct rw_semaphore leds_list_lock;
+extern struct list_head leds_list;
+
+#endif	/* __LEDS_H_INCLUDED */