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, 212 insertions, 0 deletions

diff --git a/lib/kunit/string-stream.c b/lib/kunit/string-stream.c
new file mode 100644
index 000000000..51ba40ebf
--- /dev/null
+++ b/lib/kunit/string-stream.c
@@ -0,0 +1,212 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * C++ stream style string builder used in KUnit for building messages.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#include <kunit/static_stub.h>
+#include <kunit/test.h>
+#include <linux/list.h>
+#include <linux/seq_buf.h>
+#include <linux/slab.h>
+
+#include "string-stream.h"
+
+
+static struct string_stream_fragment *alloc_string_stream_fragment(int len, gfp_t gfp)
+{
+	struct string_stream_fragment *frag;
+
+	frag = kzalloc_obj(*frag, gfp);
+	if (!frag)
+		return ERR_PTR(-ENOMEM);
+
+	frag->fragment = kmalloc(len, gfp);
+	if (!frag->fragment) {
+		kfree(frag);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	return frag;
+}
+
+static void string_stream_fragment_destroy(struct string_stream_fragment *frag)
+{
+	list_del(&frag->node);
+	kfree(frag->fragment);
+	kfree(frag);
+}
+
+int string_stream_vadd(struct string_stream *stream,
+		       const char *fmt,
+		       va_list args)
+{
+	struct string_stream_fragment *frag_container;
+	int buf_len, result_len;
+	va_list args_for_counting;
+
+	/* Make a copy because `vsnprintf` could change it */
+	va_copy(args_for_counting, args);
+
+	/* Evaluate length of formatted string */
+	buf_len = vsnprintf(NULL, 0, fmt, args_for_counting);
+
+	va_end(args_for_counting);
+
+	if (buf_len == 0)
+		return 0;
+
+	/* Reserve one extra for possible appended newline. */
+	if (stream->append_newlines)
+		buf_len++;
+
+	/* Need space for null byte. */
+	buf_len++;
+
+	frag_container = alloc_string_stream_fragment(buf_len, stream->gfp);
+	if (IS_ERR(frag_container))
+		return PTR_ERR(frag_container);
+
+	if (stream->append_newlines) {
+		/* Don't include reserved newline byte in writeable length. */
+		result_len = vsnprintf(frag_container->fragment, buf_len - 1, fmt, args);
+
+		/* Append newline if necessary. */
+		if (frag_container->fragment[result_len - 1] != '\n')
+			result_len += strscpy(frag_container->fragment + result_len,
+					      "\n", buf_len - result_len);
+	} else {
+		result_len = vsnprintf(frag_container->fragment, buf_len, fmt, args);
+	}
+
+	spin_lock(&stream->lock);
+	stream->length += result_len;
+	list_add_tail(&frag_container->node, &stream->fragments);
+	spin_unlock(&stream->lock);
+
+	return 0;
+}
+
+int string_stream_add(struct string_stream *stream, const char *fmt, ...)
+{
+	va_list args;
+	int result;
+
+	va_start(args, fmt);
+	result = string_stream_vadd(stream, fmt, args);
+	va_end(args);
+
+	return result;
+}
+
+void string_stream_clear(struct string_stream *stream)
+{
+	struct string_stream_fragment *frag_container, *frag_container_safe;
+
+	spin_lock(&stream->lock);
+	list_for_each_entry_safe(frag_container,
+				 frag_container_safe,
+				 &stream->fragments,
+				 node) {
+		string_stream_fragment_destroy(frag_container);
+	}
+	stream->length = 0;
+	spin_unlock(&stream->lock);
+}
+
+char *string_stream_get_string(struct string_stream *stream)
+{
+	struct string_stream_fragment *frag_container;
+	size_t buf_len = stream->length + 1; /* +1 for null byte. */
+	struct seq_buf sb;
+	char *buf;
+
+	buf = kzalloc(buf_len, stream->gfp);
+	if (!buf)
+		return NULL;
+
+	seq_buf_init(&sb, buf, buf_len);
+
+	spin_lock(&stream->lock);
+	list_for_each_entry(frag_container, &stream->fragments, node)
+		seq_buf_puts(&sb, frag_container->fragment);
+	spin_unlock(&stream->lock);
+
+	return buf;
+}
+
+int string_stream_append(struct string_stream *stream,
+			 struct string_stream *other)
+{
+	const char *other_content;
+	int ret;
+
+	other_content = string_stream_get_string(other);
+
+	if (!other_content)
+		return -ENOMEM;
+
+	ret = string_stream_add(stream, other_content);
+	kfree(other_content);
+
+	return ret;
+}
+
+bool string_stream_is_empty(struct string_stream *stream)
+{
+	return list_empty(&stream->fragments);
+}
+
+struct string_stream *alloc_string_stream(gfp_t gfp)
+{
+	struct string_stream *stream;
+
+	stream = kzalloc_obj(*stream, gfp);
+	if (!stream)
+		return ERR_PTR(-ENOMEM);
+
+	stream->gfp = gfp;
+	INIT_LIST_HEAD(&stream->fragments);
+	spin_lock_init(&stream->lock);
+
+	return stream;
+}
+
+void string_stream_destroy(struct string_stream *stream)
+{
+	KUNIT_STATIC_STUB_REDIRECT(string_stream_destroy, stream);
+
+	if (IS_ERR_OR_NULL(stream))
+		return;
+
+	string_stream_clear(stream);
+	kfree(stream);
+}
+
+static void resource_free_string_stream(void *p)
+{
+	struct string_stream *stream = p;
+
+	string_stream_destroy(stream);
+}
+
+struct string_stream *kunit_alloc_string_stream(struct kunit *test, gfp_t gfp)
+{
+	struct string_stream *stream;
+
+	stream = alloc_string_stream(gfp);
+	if (IS_ERR(stream))
+		return stream;
+
+	if (kunit_add_action_or_reset(test, resource_free_string_stream, stream) != 0)
+		return ERR_PTR(-ENOMEM);
+
+	return stream;
+}
+
+void kunit_free_string_stream(struct kunit *test, struct string_stream *stream)
+{
+	kunit_release_action(test, resource_free_string_stream, (void *)stream);
+}