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, 151 insertions, 0 deletions

diff --git a/net/mptcp/token_test.c b/net/mptcp/token_test.c
new file mode 100644
index 000000000..4fc39fa2e
--- /dev/null
+++ b/net/mptcp/token_test.c
@@ -0,0 +1,151 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <kunit/test.h>
+
+#include "protocol.h"
+
+static struct mptcp_subflow_request_sock *build_req_sock(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req;
+
+	req = kunit_kzalloc(test, sizeof(struct mptcp_subflow_request_sock),
+			    GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, req);
+	mptcp_token_init_request((struct request_sock *)req);
+	sock_net_set((struct sock *)req, &init_net);
+	return req;
+}
+
+static void mptcp_token_test_req_basic(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *null_msk = NULL;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	KUNIT_EXPECT_NE(test, 0, (int)req->token);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, req->token));
+
+	/* cleanup */
+	mptcp_token_destroy_request((struct request_sock *)req);
+}
+
+static struct inet_connection_sock *build_icsk(struct kunit *test)
+{
+	struct inet_connection_sock *icsk;
+
+	icsk = kunit_kzalloc(test, sizeof(struct inet_connection_sock),
+			     GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, icsk);
+	return icsk;
+}
+
+static struct mptcp_subflow_context *build_ctx(struct kunit *test)
+{
+	struct mptcp_subflow_context *ctx;
+
+	ctx = kunit_kzalloc(test, sizeof(struct mptcp_subflow_context),
+			    GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, ctx);
+	return ctx;
+}
+
+static struct mptcp_sock *build_msk(struct kunit *test)
+{
+	struct mptcp_sock *msk;
+	struct sock *sk;
+
+	msk = kunit_kzalloc(test, sizeof(struct mptcp_sock), GFP_USER);
+	KUNIT_EXPECT_NOT_ERR_OR_NULL(test, msk);
+	refcount_set(&((struct sock *)msk)->sk_refcnt, 1);
+	sock_net_set((struct sock *)msk, &init_net);
+
+	sk = (struct sock *)msk;
+
+	/* be sure the token helpers can dereference sk->sk_prot */
+	sk->sk_prot = &tcp_prot;
+	sk->sk_protocol = IPPROTO_MPTCP;
+
+	return msk;
+}
+
+static void mptcp_token_test_msk_basic(struct kunit *test)
+{
+	struct inet_connection_sock *icsk = build_icsk(test);
+	struct mptcp_subflow_context *ctx = build_ctx(test);
+	struct mptcp_sock *msk = build_msk(test);
+	struct mptcp_sock *null_msk = NULL;
+	struct sock *sk;
+
+	rcu_assign_pointer(icsk->icsk_ulp_data, ctx);
+	ctx->conn = (struct sock *)msk;
+	sk = (struct sock *)msk;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_connect((struct sock *)icsk));
+	KUNIT_EXPECT_NE(test, 0, (int)ctx->token);
+	KUNIT_EXPECT_EQ(test, ctx->token, msk->token);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, ctx->token));
+	KUNIT_EXPECT_EQ(test, 2, (int)refcount_read(&sk->sk_refcnt));
+
+	mptcp_token_destroy(msk);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, ctx->token));
+}
+
+static void mptcp_token_test_accept(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *msk = build_msk(test);
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	msk->token = req->token;
+	mptcp_token_accept(req, msk);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, msk->token));
+
+	/* this is now a no-op */
+	mptcp_token_destroy_request((struct request_sock *)req);
+	KUNIT_EXPECT_PTR_EQ(test, msk, mptcp_token_get_sock(&init_net, msk->token));
+
+	/* cleanup */
+	mptcp_token_destroy(msk);
+}
+
+static void mptcp_token_test_destroyed(struct kunit *test)
+{
+	struct mptcp_subflow_request_sock *req = build_req_sock(test);
+	struct mptcp_sock *msk = build_msk(test);
+	struct mptcp_sock *null_msk = NULL;
+	struct sock *sk;
+
+	sk = (struct sock *)msk;
+
+	KUNIT_ASSERT_EQ(test, 0,
+			mptcp_token_new_request((struct request_sock *)req));
+	msk->token = req->token;
+	mptcp_token_accept(req, msk);
+
+	/* simulate race on removal */
+	refcount_set(&sk->sk_refcnt, 0);
+	KUNIT_EXPECT_PTR_EQ(test, null_msk, mptcp_token_get_sock(&init_net, msk->token));
+
+	/* cleanup */
+	mptcp_token_destroy(msk);
+}
+
+static struct kunit_case mptcp_token_test_cases[] = {
+	KUNIT_CASE(mptcp_token_test_req_basic),
+	KUNIT_CASE(mptcp_token_test_msk_basic),
+	KUNIT_CASE(mptcp_token_test_accept),
+	KUNIT_CASE(mptcp_token_test_destroyed),
+	{}
+};
+
+static struct kunit_suite mptcp_token_suite = {
+	.name = "mptcp-token",
+	.test_cases = mptcp_token_test_cases,
+};
+
+kunit_test_suite(mptcp_token_suite);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("KUnit tests for MPTCP Token");