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, 91 insertions, 0 deletions

diff --git a/lib/kunit/try-catch.c b/lib/kunit/try-catch.c
new file mode 100644
index 000000000..d84a879f0
--- /dev/null
+++ b/lib/kunit/try-catch.c
@@ -0,0 +1,91 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * An API to allow a function, that may fail, to be executed, and recover in a
+ * controlled manner.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#include <kunit/test.h>
+#include <linux/completion.h>
+#include <linux/kernel.h>
+#include <linux/kthread.h>
+#include <linux/sched/task.h>
+
+#include "try-catch-impl.h"
+
+void __noreturn kunit_try_catch_throw(struct kunit_try_catch *try_catch)
+{
+	try_catch->try_result = -EFAULT;
+	kthread_exit(0);
+}
+EXPORT_SYMBOL_GPL(kunit_try_catch_throw);
+
+static int kunit_generic_run_threadfn_adapter(void *data)
+{
+	struct kunit_try_catch *try_catch = data;
+
+	try_catch->try_result = -EINTR;
+	try_catch->try(try_catch->context);
+	if (try_catch->try_result == -EINTR)
+		try_catch->try_result = 0;
+
+	return 0;
+}
+
+void kunit_try_catch_run(struct kunit_try_catch *try_catch, void *context)
+{
+	struct kunit *test = try_catch->test;
+	struct task_struct *task_struct;
+	struct completion *task_done;
+	int exit_code, time_remaining;
+
+	try_catch->context = context;
+	try_catch->try_result = 0;
+	task_struct = kthread_create(kunit_generic_run_threadfn_adapter,
+				     try_catch, "kunit_try_catch_thread");
+	if (IS_ERR(task_struct)) {
+		try_catch->try_result = PTR_ERR(task_struct);
+		try_catch->catch(try_catch->context);
+		return;
+	}
+	get_task_struct(task_struct);
+	/*
+	 * As for a vfork(2), task_struct->vfork_done (pointing to the
+	 * underlying kthread->exited) can be used to wait for the end of a
+	 * kernel thread. It is set to NULL when the thread exits, so we
+	 * keep a copy here.
+	 */
+	task_done = task_struct->vfork_done;
+	wake_up_process(task_struct);
+
+	time_remaining = wait_for_completion_timeout(
+		task_done, try_catch->timeout);
+	if (time_remaining == 0) {
+		try_catch->try_result = -ETIMEDOUT;
+		kthread_stop(task_struct);
+	}
+
+	put_task_struct(task_struct);
+	exit_code = try_catch->try_result;
+
+	if (!exit_code)
+		return;
+
+	if (exit_code == -EFAULT)
+		try_catch->try_result = 0;
+	else if (exit_code == -EINTR) {
+		if (test->last_seen.file)
+			kunit_err(test, "try faulted: last line seen %s:%d\n",
+				  test->last_seen.file, test->last_seen.line);
+		else
+			kunit_err(test, "try faulted\n");
+	} else if (exit_code == -ETIMEDOUT)
+		kunit_err(test, "try timed out\n");
+	else if (exit_code)
+		kunit_err(test, "Unknown error: %d\n", exit_code);
+
+	try_catch->catch(try_catch->context);
+}
+EXPORT_SYMBOL_GPL(kunit_try_catch_run);