[PATCH v2 2/3] 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 leaves the attribute
unchanged, and that LANDLOCK_RESTRICT_SELF_TSYNC extends it to sibling
threads.  Also check that this flag requires a ruleset, and update the
restrict_self_checks_ordering EPERM checks since this flag is now
checked before the flags validity.

Update the ABI version and last-flag checks accordingly.

Signed-off-by: Justin Suess <utilityemal77@gmail.com>
---
 tools/testing/selftests/landlock/base_test.c  | 65 +++++++++++++++++--
 tools/testing/selftests/landlock/tsync_test.c | 33 ++++++++++
 2 files changed, 93 insertions(+), 5 deletions(-)

diff --git a/tools/testing/selftests/landlock/base_test.c b/tools/testing/selftests/landlock/base_test.c
index cbd3c1669951..2d4903588903 100644
--- a/tools/testing/selftests/landlock/base_test.c
+++ b/tools/testing/selftests/landlock/base_test.c
@@ -76,7 +76,7 @@ TEST(abi_version)
 	const struct landlock_ruleset_attr ruleset_attr = {
 		.handled_access_fs = LANDLOCK_ACCESS_FS_READ_FILE,
 	};
-	ASSERT_EQ(10, landlock_create_ruleset(NULL, 0,
+	ASSERT_EQ(11, landlock_create_ruleset(NULL, 0,
 					      LANDLOCK_CREATE_RULESET_VERSION));
 
 	ASSERT_EQ(-1, landlock_create_ruleset(&ruleset_attr, 0,
@@ -255,8 +255,15 @@ TEST(restrict_self_checks_ordering)
 
 	/* Checks unprivileged enforcement without no_new_privs. */
 	drop_caps(_metadata);
-	ASSERT_EQ(-1, landlock_restrict_self(-1, -1));
+	ASSERT_EQ(-1, landlock_restrict_self(
+			      -1, ~LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
 	ASSERT_EQ(EPERM, errno);
+	/*
+	 * LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS fulfills the no_new_privs /
+	 * CAP_SYS_ADMIN requirement, so the invalid flags are checked first.
+	 */
+	ASSERT_EQ(-1, landlock_restrict_self(-1, -1));
+	ASSERT_EQ(EINVAL, errno);
 	ASSERT_EQ(-1, landlock_restrict_self(-1, 0));
 	ASSERT_EQ(EPERM, errno);
 	ASSERT_EQ(-1, landlock_restrict_self(ruleset_fd, 0));
@@ -288,7 +295,7 @@ TEST(restrict_self_fd)
 	EXPECT_EQ(EBADFD, errno);
 }
 
-TEST(restrict_self_fd_logging_flags)
+TEST(restrict_self_fd_flags)
 {
 	int fd;
 
@@ -302,11 +309,16 @@ 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_TSYNC;
+	const __u32 last_flag = LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS;
 
 	/* Tests invalid flag combinations. */
 
@@ -349,6 +361,18 @@ 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(
@@ -359,6 +383,37 @@ 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..d5336186b2c7 100644
--- a/tools/testing/selftests/landlock/tsync_test.c
+++ b/tools/testing/selftests/landlock/tsync_test.c
@@ -90,6 +90,39 @@ TEST(multi_threaded_success)
 	EXPECT_EQ(0, close(ruleset_fd));
 }
 
+TEST(multi_threaded_no_new_privs)
+{
+	pthread_t t1, t2;
+	bool no_new_privs1, no_new_privs2;
+	const int ruleset_fd = create_ruleset(_metadata);
+
+	disable_caps(_metadata);
+
+	ASSERT_EQ(0, pthread_create(&t1, NULL, idle, &no_new_privs1));
+	ASSERT_EQ(0, pthread_create(&t2, NULL, idle, &no_new_privs2));
+
+	/* 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 |
+				     LANDLOCK_RESTRICT_SELF_NO_NEW_PRIVS));
+
+	EXPECT_EQ(1, 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 enabled on all threads. */
+	EXPECT_TRUE(no_new_privs1);
+	EXPECT_TRUE(no_new_privs2);
+
+	EXPECT_EQ(0, close(ruleset_fd));
+}
+
 TEST(multi_threaded_success_despite_diverging_domains)
 {
 	pthread_t t1, t2;
-- 
2.54.0