Add test that validates Landlock behaviour with overlapped socket
restriction.

Add test that validates behaviour of using multiple layers that
define access for protocol ranges using wildcard values.

Signed-off-by: Mikhail Ivanov <ivanov.mikhail1@huawei-partners.com>
---
Changes since v3:
* Adds test "ruleset_with_wildcards_overlap".

Changes since v2:
* Removes `tcp_layers` fixture and replaces it with `protocol` fixture
  for this test. protocol.ruleset_overlap tests every layers depth
  in a single run.
* Adds add_ruleset_layer() helper that enforces ruleset and allows access
  if such is given.
* Replaces EXPECT_EQ with ASSERT_EQ for close().
* Refactors commit message and title.

Changes since v1:
* Replaces test_socket_create() with test_socket().
* Formats code with clang-format.
* Refactors commit message.
* Minor fixes.
---
 .../testing/selftests/landlock/socket_test.c  | 92 +++++++++++++++++++
 1 file changed, 92 insertions(+)

diff --git a/tools/testing/selftests/landlock/socket_test.c b/tools/testing/selftests/landlock/socket_test.c
index ebb39cbf9211..8b8913290a64 100644
--- a/tools/testing/selftests/landlock/socket_test.c
+++ b/tools/testing/selftests/landlock/socket_test.c
@@ -578,4 +578,96 @@ TEST_F(mini, unsupported_af_and_prot)
 	EXPECT_EQ(EACCES, test_socket(AF_UNIX, SOCK_STREAM, PF_UNIX + 1));
 }
 
+static void add_ruleset_layer(struct __test_metadata *const _metadata,
+			      const struct landlock_socket_attr *socket_attr)
+{
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_socket = LANDLOCK_ACCESS_SOCKET_CREATE,
+	};
+	int ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	if (socket_attr) {
+		ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_SOCKET,
+					       socket_attr, 0));
+	}
+
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+}
+
+TEST_F(mini, ruleset_overlap)
+{
+	const struct landlock_socket_attr create_socket_attr = {
+		.allowed_access = LANDLOCK_ACCESS_SOCKET_CREATE,
+		.family = AF_INET,
+		.type = SOCK_STREAM,
+		.protocol = 0,
+	};
+
+	/* socket(2) is allowed if there are no restrictions. */
+	ASSERT_EQ(0, test_socket(AF_INET, SOCK_STREAM, 0));
+
+	/* Creates ruleset with socket(2) allowed. */
+	add_ruleset_layer(_metadata, &create_socket_attr);
+	EXPECT_EQ(0, test_socket(AF_INET, SOCK_STREAM, 0));
+
+	/* Adds ruleset layer with socket(2) restricted. */
+	add_ruleset_layer(_metadata, NULL);
+	EXPECT_EQ(EACCES, test_socket(AF_INET, SOCK_STREAM, 0));
+
+	/*
+	 * Adds ruleset layer with socket(2) allowed. socket(2) is restricted
+	 * by second layer of the ruleset.
+	 */
+	add_ruleset_layer(_metadata, &create_socket_attr);
+	EXPECT_EQ(EACCES, test_socket(AF_INET, SOCK_STREAM, 0));
+}
+
+TEST_F(mini, ruleset_with_wildcards_overlap)
+{
+	const struct landlock_socket_attr create_socket_attr = {
+		.allowed_access = LANDLOCK_ACCESS_SOCKET_CREATE,
+		.family = AF_INET,
+		.type = (-1),
+		.protocol = (-1),
+	};
+
+	/* socket(2) is allowed if there are no restrictions. */
+	ASSERT_EQ(0, test_socket(AF_INET, SOCK_STREAM, 0));
+	ASSERT_EQ(0, test_socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP));
+	ASSERT_EQ(0, test_socket(AF_INET, SOCK_DGRAM, 0));
+
+	/* Creates ruleset with AF_INET allowed. */
+	add_ruleset_layer(_metadata, &create_socket_attr);
+	EXPECT_EQ(0, test_socket(AF_INET, SOCK_STREAM, 0));
+	EXPECT_EQ(0, test_socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP));
+	EXPECT_EQ(0, test_socket(AF_INET, SOCK_DGRAM, 0));
+
+	const struct landlock_socket_attr create_socket_attr2 = {
+		.allowed_access = LANDLOCK_ACCESS_SOCKET_CREATE,
+		.family = AF_INET,
+		.type = SOCK_STREAM,
+		.protocol = (-1),
+	};
+	/* Creates layer with AF_INET + SOCK_STREAM allowed. */
+	add_ruleset_layer(_metadata, &create_socket_attr2);
+	EXPECT_EQ(0, test_socket(AF_INET, SOCK_STREAM, 0));
+	EXPECT_EQ(0, test_socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP));
+	EXPECT_EQ(EACCES, test_socket(AF_INET, SOCK_DGRAM, 0));
+
+	const struct landlock_socket_attr create_socket_attr3 = {
+		.allowed_access = LANDLOCK_ACCESS_SOCKET_CREATE,
+		.family = AF_INET,
+		.type = SOCK_STREAM,
+		.protocol = 0,
+	};
+	/* Creates layer with AF_INET + SOCK_STREAM + 0 allowed. */
+	add_ruleset_layer(_metadata, &create_socket_attr3);
+	EXPECT_EQ(0, test_socket(AF_INET, SOCK_STREAM, 0));
+	EXPECT_EQ(EACCES, test_socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP));
+	EXPECT_EQ(EACCES, test_socket(AF_INET, SOCK_DGRAM, 0));
+}
+
 TEST_HARNESS_MAIN
-- 
2.34.1