[PATCH v4 5/7] selftests/landlock: Test ioctl(2) and ftruncate(2) with open(O_PATH)

[Günther Noack]

ioctl(2) and ftruncate(2) operations on files opened with O_PATH
should always return EBADF, independent of the
LANDLOCK_ACCESS_FS_TRUNCATE and LANDLOCK_ACCESS_FS_IOCTL access rights
in that file hierarchy.

Signed-off-by: Günther Noack <gnoack at google.com>
Suggested-by: Mickaël Salaün <mic at digikod.net>
---
 tools/testing/selftests/landlock/fs_test.c | 40 ++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/tools/testing/selftests/landlock/fs_test.c b/tools/testing/selftests/landlock/fs_test.c
index 8a244c9cd030..06c47c816c51 100644
--- a/tools/testing/selftests/landlock/fs_test.c
+++ b/tools/testing/selftests/landlock/fs_test.c
@@ -3812,6 +3812,46 @@ TEST(memfd_ftruncate_and_ioctl)
 	}
 }
 
+TEST_F_FORK(layout1, o_path_ftruncate_and_ioctl)
+{
+	const struct landlock_ruleset_attr attr = {
+		.handled_access_fs = ACCESS_ALL,
+	};
+	int ruleset_fd, fd;
+
+	/*
+	 * Checks that for files opened with O_PATH, both ioctl(2) and
+	 * ftruncate(2) yield EBADF, as it is documented in open(2) for the
+	 * O_PATH flag.
+	 */
+	fd = open(dir_s1d1, O_PATH | O_CLOEXEC);
+	ASSERT_LE(0, fd);
+
+	EXPECT_EQ(EBADF, test_ftruncate(fd));
+	EXPECT_EQ(EBADF, test_fs_ioc_getflags_ioctl(fd));
+
+	ASSERT_EQ(0, close(fd));
+
+	/* Enables Landlock. */
+	ruleset_fd = landlock_create_ruleset(&attr, sizeof(attr), 0);
+	ASSERT_LE(0, ruleset_fd);
+	enforce_ruleset(_metadata, ruleset_fd);
+	ASSERT_EQ(0, close(ruleset_fd));
+
+	/*
+	 * Checks that after enabling Landlock,
+	 * - the file can still be opened with O_PATH
+	 * - both ioctl and truncate still yield EBADF (not EACCES).
+	 */
+	fd = open(dir_s1d1, O_PATH | O_CLOEXEC);
+	ASSERT_LE(0, fd);
+
+	EXPECT_EQ(EBADF, test_ftruncate(fd));
+	EXPECT_EQ(EBADF, test_fs_ioc_getflags_ioctl(fd));
+
+	ASSERT_EQ(0, close(fd));
+}
+
 /* clang-format off */
 FIXTURE(ioctl) {};
 /* clang-format on */
-- 
2.42.0.869.gea05f2083d-goog