[PATCH v4 3/5] selftests/landlock: Test LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS

[Justin Suess <utilityemal77@gmail.com>]

Check that a successful landlock_restrict_self(2) call with
LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS sets no_new_privs without a prior
prctl(2) call nor CAP_SYS_ADMIN, that a failed call from both an
invalid ruleset and hitting the layer maximum leaves the attribute
unchanged, and that LANDLOCK_RESTRICT_SELF_TSYNC extends it to sibling
threads.  Also check that this flag requires a ruleset.

Turn the multi_threaded_success test into a multi_threaded fixture with
success, no_new_privs, and no_new_privs_max_layers variants to factor
out the threading code.

Finally, rename restrict_self_fd_logging_flags to
restrict_self_fd_flags, and restrict_self_logging_flags to
restrict_self_flags to indicate that non-logging flags are now tested.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---

Notes:
    v3->v4:
        - Turn multi_threaded_{success,no_new_privs,no_new_privs_max_layers}
          into variants of a multi_threaded fixture, per Mickaël's
          feedback.
        - Move the minimal ABI/flag checks into the previous patch.

 tools/testing/selftests/landlock/base_test.c  | 86 ++++++++++++++++-
 tools/testing/selftests/landlock/tsync_test.c | 96 ++++++++++++++++---
 2 files changed, 168 insertions(+), 14 deletions(-)

diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index 288d6bc19232..d20ab8f0862c 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -289,6 +289,41 @@ TEST(restrict_self_checks_ordering)
 	ASSERT_EQ(0, close(ruleset_fd));
 }
 
+TEST(restrict_self_max_layers)
+{
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = LANDLOCK_ACCESS_FS_EXECUTE,
+	};
+	struct landlock_path_beneath_attr path_beneath_attr = {
+		.allowed_access = LANDLOCK_ACCESS_FS_EXECUTE,
+		.parent_fd = -1,
+	};
+	const int ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+
+	path_beneath_attr.parent_fd =
+		open("/tmp", O_PATH | O_NOFOLLOW | O_DIRECTORY | O_CLOEXEC);
+	ASSERT_LE(0, path_beneath_attr.parent_fd);
+	ASSERT_EQ(0, landlock_add_rule(ruleset_fd, LANDLOCK_RULE_PATH_BENEATH,
+				       &path_beneath_attr, 0));
+	ASSERT_EQ(0, close(path_beneath_attr.parent_fd));
+
+	/* Enforces the maximum number of allowed layers. */
+	for (int i = 0; i < LANDLOCK_MAX_NUM_LAYERS; i++)
+		ASSERT_EQ(0, landlock_restrict_self(ruleset_fd, 0));
+
+	/* Enforces one too many rulesets. */
+	drop_caps(_metadata);
+	ASSERT_EQ(-1, landlock_restrict_self(
+			      ruleset_fd, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	ASSERT_EQ(E2BIG, errno);
+
+	/* Checks that the failed call did not set no_new_privs. */
+	ASSERT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+	ASSERT_EQ(0, close(ruleset_fd));
+}
+
 TEST(restrict_self_fd)
 {
 	int fd;
@@ -300,7 +335,7 @@ TEST(restrict_self_fd)
 	EXPECT_EQ(EBADFD, errno);
 }
 
-TEST(restrict_self_fd_logging_flags)
+TEST(restrict_self_fd_flags)
 {
 	int fd;
 
@@ -314,9 +349,14 @@ TEST(restrict_self_fd_logging_flags)
 	EXPECT_EQ(-1, landlock_restrict_self(
 			      fd, LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF));
 	EXPECT_EQ(EBADFD, errno);
+
+	/* LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS requires a ruleset FD. */
+	EXPECT_EQ(-1, landlock_restrict_self(
+			      fd, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(EBADFD, errno);
 }
 
-TEST(restrict_self_logging_flags)
+TEST(restrict_self_flags)
 {
 	const __u32 last_flag = LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS;
 
@@ -361,6 +401,17 @@ TEST(restrict_self_logging_flags)
 				      LANDLOCK_RESTRICT_SELF_LOG_NEW_EXEC_ON));
 	EXPECT_EQ(EBADF, errno);
 
+	/* LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS requires a ruleset FD. */
+
+	EXPECT_EQ(-1, landlock_restrict_self(
+			      -1, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(EBADF, errno);
+
+	EXPECT_EQ(-1, landlock_restrict_self(
+			      -1, LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF |
+					  LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(EBADF, errno);
+
 	/* Tests with an invalid ruleset_fd. */
 
 	EXPECT_EQ(-1, landlock_restrict_self(
@@ -371,6 +422,37 @@ TEST(restrict_self_logging_flags)
 			     -1, LANDLOCK_RESTRICT_SELF_LOG_SUBDOMAINS_OFF));
 }
 
+TEST(restrict_self_no_new_privs)
+{
+	const struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
+	};
+	const int ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+
+	ASSERT_LE(0, ruleset_fd);
+
+	/*
+	 * The calling thread does not need CAP_SYS_ADMIN nor an explicit
+	 * prctl(2) PR_SET_NO_NEW_PRIVS call.
+	 */
+	drop_caps(_metadata);
+	ASSERT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	/* Checks that a failed call does not set no_new_privs. */
+	EXPECT_EQ(-1, landlock_restrict_self(
+			      -1, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(EBADF, errno);
+	EXPECT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	/* Checks that a successful call sets no_new_privs. */
+	ASSERT_EQ(0, landlock_restrict_self(
+			     ruleset_fd, LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+	EXPECT_EQ(1, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
 TEST(ruleset_fd_io)
 {
 	struct landlock_ruleset_attr ruleset_attr = {
diff --git a/tools/testing/selftests/landlock/tsync_test.c b/tools/testing/selftests/landlock/tsync_test.c
index 9cf1491bbaaf..2b53596c986e 100644
--- a/tools/testing/selftests/landlock/tsync_test.c
+++ b/tools/testing/selftests/landlock/tsync_test.c
@@ -62,32 +62,104 @@ static void *idle(void *data)
 	pthread_cleanup_pop(1);
 }
 
-TEST(multi_threaded_success)
+FIXTURE(multi_threaded)
 {
-	pthread_t t1, t2;
-	bool no_new_privs1, no_new_privs2;
-	const int ruleset_fd = create_ruleset(_metadata);
+	int ruleset_fd;
+};
+
+FIXTURE_VARIANT(multi_threaded)
+{
+	const __u32 restrict_flags;
+	/* Sets no_new_privs with prctl(2) before the enforcement. */
+	const bool prior_no_new_privs;
+	/* Enforces the maximum number of allowed layers beforehand. */
+	const bool max_layers;
+	const int expected_errno;
+	/* Expected no_new_privs state of all threads after the call. */
+	const bool expected_no_new_privs;
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(multi_threaded, success) {
+	/* clang-format on */
+	.restrict_flags = LANDLOCK_RESTRICT_SELF_TSYNC,
+	.prior_no_new_privs = true,
+	.expected_no_new_privs = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(multi_threaded, no_new_privs) {
+	/* clang-format on */
+	.restrict_flags = LANDLOCK_RESTRICT_SELF_TSYNC |
+			  LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS,
+	.expected_no_new_privs = true,
+};
+
+/* clang-format off */
+FIXTURE_VARIANT_ADD(multi_threaded, no_new_privs_max_layers) {
+	/* clang-format on */
+	.restrict_flags = LANDLOCK_RESTRICT_SELF_TSYNC |
+			  LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS,
+	.max_layers = true,
+	.expected_errno = E2BIG,
+	.expected_no_new_privs = false,
+};
+
+FIXTURE_SETUP(multi_threaded)
+{
+	self->ruleset_fd = create_ruleset(_metadata);
+
+	if (variant->max_layers) {
+		/* Enforces the maximum number of allowed layers. */
+		for (int i = 0; i < LANDLOCK_MAX_NUM_LAYERS; i++)
+			ASSERT_EQ(0,
+				  landlock_restrict_self(self->ruleset_fd, 0));
+	}
 
 	disable_caps(_metadata);
+}
+
+FIXTURE_TEARDOWN(multi_threaded)
+{
+	EXPECT_EQ(0, close(self->ruleset_fd));
+}
+
+TEST_F(multi_threaded, restrict)
+{
+	pthread_t t1, t2;
+	bool no_new_privs1, no_new_privs2;
 
 	ASSERT_EQ(0, pthread_create(&t1, NULL, idle, &no_new_privs1));
 	ASSERT_EQ(0, pthread_create(&t2, NULL, idle, &no_new_privs2));
 
-	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+	if (variant->prior_no_new_privs) {
+		ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+	} else {
+		/* No prior prctl(2) PR_SET_NO_NEW_PRIVS call. */
+		ASSERT_EQ(0, prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
+	}
 
-	EXPECT_EQ(0, landlock_restrict_self(ruleset_fd,
-					    LANDLOCK_RESTRICT_SELF_TSYNC));
+	if (variant->expected_errno) {
+		EXPECT_EQ(-1, landlock_restrict_self(self->ruleset_fd,
+						     variant->restrict_flags));
+		EXPECT_EQ(variant->expected_errno, errno);
+	} else {
+		EXPECT_EQ(0, landlock_restrict_self(self->ruleset_fd,
+						    variant->restrict_flags));
+	}
+
+	/* Checks the no_new_privs state of the calling thread. */
+	EXPECT_EQ(variant->expected_no_new_privs,
+		  prctl(PR_GET_NO_NEW_PRIVS, 0, 0, 0, 0));
 
 	ASSERT_EQ(0, pthread_cancel(t1));
 	ASSERT_EQ(0, pthread_cancel(t2));
 	ASSERT_EQ(0, pthread_join(t1, NULL));
 	ASSERT_EQ(0, pthread_join(t2, NULL));
 
-	/* The no_new_privs flag was implicitly enabled on all threads. */
-	EXPECT_TRUE(no_new_privs1);
-	EXPECT_TRUE(no_new_privs2);
-
-	EXPECT_EQ(0, close(ruleset_fd));
+	/* Checks the no_new_privs state of the sibling threads. */
+	EXPECT_EQ(variant->expected_no_new_privs, no_new_privs1);
+	EXPECT_EQ(variant->expected_no_new_privs, no_new_privs2);
 }
 
 TEST(multi_threaded_success_despite_diverging_domains)
-- 
2.55.0