[RFC,2/2] landlock: selftests for LANDLOCK_RESTRICT_SELF_TSYNC

Commit Message

Günther Noack Feb. 21, 2025, 6:44 p.m. UTC

Exercise various scenarios where Landlock domains are enforced across
all of a processes' threads.

Signed-off-by: Günther Noack <[e-mail]>
---
 tools/testing/selftests/landlock/tsync_test.c | 94 +++++++++++++++++++
 1 file changed, 94 insertions(+)
 create mode 100644 tools/testing/selftests/landlock/tsync_test.c

Patch

diff --git a/tools/testing/selftests/landlock/tsync_test.c b/tools/testing/selftests/landlock/tsync_test.c
new file mode 100644
index 0000000000000..e8261a58c13ba
--- /dev/null
+++ b/tools/testing/selftests/landlock/tsync_test.c
@@ -0,0 +1,94 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Landlock tests - Enforcing the same restrictions across multiple threads
+ *
+ * Copyright © 2025 Günther Noack <[e-mail]>
+ */
+
+#define _GNU_SOURCE
+#include <pthread.h>
+#include <sys/prctl.h>
+#include <linux/landlock.h>
+
+#include "common.h"
+
+/* create_ruleset - Create a simple ruleset FD common to all tests */
+static int create_ruleset(struct __test_metadata *const _metadata)
+{
+	struct landlock_ruleset_attr ruleset_attr = {
+		.handled_access_fs = (LANDLOCK_ACCESS_FS_WRITE_FILE |
+				      LANDLOCK_ACCESS_FS_TRUNCATE),
+	};
+	const int ruleset_fd =
+		landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0);
+
+	ASSERT_LE(0, ruleset_fd);
+	return ruleset_fd;
+}
+
+TEST(single_threaded_success)
+{
+	const int ruleset_fd = create_ruleset(_metadata);
+
+	disable_caps(_metadata);
+
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+	ASSERT_EQ(0, landlock_restrict_self(ruleset_fd,
+					    LANDLOCK_RESTRICT_SELF_TSYNC));
+
+	ASSERT_EQ(0, close(ruleset_fd));
+}
+
+void *idle(void *data)
+{
+	while (true)
+		sleep(1);
+}
+
+TEST(multi_threaded_success)
+{
+	pthread_t t1, t2;
+	const int ruleset_fd = create_ruleset(_metadata);
+
+	disable_caps(_metadata);
+
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+
+	ASSERT_EQ(0, pthread_create(&t1, NULL, idle, NULL));
+	ASSERT_EQ(0, pthread_create(&t2, NULL, idle, NULL));
+
+	EXPECT_EQ(0, landlock_restrict_self(ruleset_fd,
+					    LANDLOCK_RESTRICT_SELF_TSYNC));
+
+	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));
+	ASSERT_EQ(0, close(ruleset_fd));
+}
+
+TEST(multi_threaded_failure)
+{
+	pthread_t t1;
+	const int ruleset_fd = create_ruleset(_metadata);
+
+	disable_caps(_metadata);
+
+	ASSERT_EQ(0, pthread_create(&t1, NULL, idle, NULL));
+
+	/*
+	 * landlock_restrict_self is expected to fail, because the other thread
+	 * has neither the NO_NEW_PRIVS flag nor CAP_SYS_ADMIN, and thus, it may
+	 * not enforce the Landlock ruleset.
+	 */
+	ASSERT_EQ(0, prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0));
+	EXPECT_EQ(-1, landlock_restrict_self(ruleset_fd,
+					     LANDLOCK_RESTRICT_SELF_TSYNC));
+	EXPECT_EQ(errno, EPERM);
+
+	ASSERT_EQ(0, pthread_cancel(t1));
+	ASSERT_EQ(0, pthread_join(t1, NULL));
+	ASSERT_EQ(0, close(ruleset_fd));
+}
+
+TEST_HARNESS_MAIN