Merge branch 'bpf-fix-recursive-lock-and-add-test'

Jiayuan Chen says:

====================
bpf: fix recursive lock and add test

1. fix recursive lock when ebpf prog return SK_PASS.
2. add selftest to reproduce recursive lock.

Note that the test code can reproduce the 'dead-lock' and if just
the selftest merged without first patch, the test case will
definitely fail, because the issue of deadlock is inevitable.

v1: https://lore.kernel.org/55fc6114-7e64-4b65-86d2-92cfd1e9e92f@linux.dev/
====================

Acked-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20241118030910.36230-1-mrpre@163.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

net/core/skmsg.c

@@ -1117,9 +1117,9 @@ static void sk_psock_strp_data_ready(struct sock *sk)
 		if (tls_sw_has_ctx_rx(sk)) {
 			psock->saved_data_ready(sk);
 		} else {
-			write_lock_bh(&sk->sk_callback_lock);
+			read_lock_bh(&sk->sk_callback_lock);
 			strp_data_ready(&psock->strp);
-			write_unlock_bh(&sk->sk_callback_lock);
+			read_unlock_bh(&sk->sk_callback_lock);
 		}
 	}
 	rcu_read_unlock();

tools/testing/selftests/bpf/prog_tests/sockmap_basic.c

@@ -501,6 +501,58 @@ static void test_sockmap_skb_verdict_shutdown(void)
 	test_sockmap_pass_prog__destroy(skel);
 }
 
+static void test_sockmap_stream_pass(void)
+{
+	int zero = 0, sent, recvd;
+	int verdict, parser;
+	int err, map;
+	int c = -1, p = -1;
+	struct test_sockmap_pass_prog *pass = NULL;
+	char snd[256] = "0123456789";
+	char rcv[256] = "0";
+
+	pass = test_sockmap_pass_prog__open_and_load();
+	verdict = bpf_program__fd(pass->progs.prog_skb_verdict);
+	parser = bpf_program__fd(pass->progs.prog_skb_parser);
+	map = bpf_map__fd(pass->maps.sock_map_rx);
+
+	err = bpf_prog_attach(parser, map, BPF_SK_SKB_STREAM_PARSER, 0);
+	if (!ASSERT_OK(err, "bpf_prog_attach stream parser"))
+		goto out;
+
+	err = bpf_prog_attach(verdict, map, BPF_SK_SKB_STREAM_VERDICT, 0);
+	if (!ASSERT_OK(err, "bpf_prog_attach stream verdict"))
+		goto out;
+
+	err = create_pair(AF_INET, SOCK_STREAM, &c, &p);
+	if (err)
+		goto out;
+
+	/* sk_data_ready of 'p' will be replaced by strparser handler */
+	err = bpf_map_update_elem(map, &zero, &p, BPF_NOEXIST);
+	if (!ASSERT_OK(err, "bpf_map_update_elem(p)"))
+		goto out_close;
+
+	/*
+	 * as 'prog_skb_parser' return the original skb len and
+	 * 'prog_skb_verdict' return SK_PASS, the kernel will just
+	 * pass it through to original socket 'p'
+	 */
+	sent = xsend(c, snd, sizeof(snd), 0);
+	ASSERT_EQ(sent, sizeof(snd), "xsend(c)");
+
+	recvd = recv_timeout(p, rcv, sizeof(rcv), SOCK_NONBLOCK,
+			     IO_TIMEOUT_SEC);
+	ASSERT_EQ(recvd, sizeof(rcv), "recv_timeout(p)");
+
+out_close:
+	close(c);
+	close(p);
+
+out:
+	test_sockmap_pass_prog__destroy(pass);
+}
+
 static void test_sockmap_skb_verdict_fionread(bool pass_prog)
 {
 	int err, map, verdict, c0 = -1, c1 = -1, p0 = -1, p1 = -1;
@@ -923,6 +975,8 @@ void test_sockmap_basic(void)
 		test_sockmap_progs_query(BPF_SK_SKB_VERDICT);
 	if (test__start_subtest("sockmap skb_verdict shutdown"))
 		test_sockmap_skb_verdict_shutdown();
+	if (test__start_subtest("sockmap stream parser and verdict pass"))
+		test_sockmap_stream_pass();
 	if (test__start_subtest("sockmap skb_verdict fionread"))
 		test_sockmap_skb_verdict_fionread(true);
 	if (test__start_subtest("sockmap skb_verdict fionread on drop"))