selftests/landlock: Test IOCTLs on named pipes

Named pipes should behave like pipes created with pipe(2),
so we don't want to restrict IOCTLs on them.
Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240419161122.2023765-6-gnoack@google.comSigned-off-by: Mickaël Salaün <mic@digikod.net>

tools/testing/selftests/landlock/fs_test.c

@@ -3942,6 +3942,49 @@ TEST_F_FORK(layout1, o_path_ftruncate_and_ioctl)
 	ASSERT_EQ(0, close(fd));
 }
 
+/*
+ * Named pipes are not governed by the LANDLOCK_ACCESS_FS_IOCTL_DEV right,
+ * because they are not character or block devices.
+ */
+TEST_F_FORK(layout1, named_pipe_ioctl)
+{
+	pid_t child_pid;
+	int fd, ruleset_fd;
+	const char *const path = file1_s1d1;
+	const struct landlock_ruleset_attr attr = {
+		.handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+	};
+
+	ASSERT_EQ(0, unlink(path));
+	ASSERT_EQ(0, mkfifo(path, 0600));
+
+	/* 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));
+
+	/* The child process opens the pipe for writing. */
+	child_pid = fork();
+	ASSERT_NE(-1, child_pid);
+	if (child_pid == 0) {
+		fd = open(path, O_WRONLY);
+		close(fd);
+		exit(0);
+	}
+
+	fd = open(path, O_RDONLY);
+	ASSERT_LE(0, fd);
+
+	/* FIONREAD is implemented by pipefifo_fops. */
+	EXPECT_EQ(0, test_fionread_ioctl(fd));
+
+	ASSERT_EQ(0, close(fd));
+	ASSERT_EQ(0, unlink(path));
+
+	ASSERT_EQ(child_pid, waitpid(child_pid, NULL, 0));
+}
+
 /* clang-format off */
 FIXTURE(ioctl) {};