selftests/landlock: Check IOCTL restrictions for named UNIX domain sockets

The LANDLOCK_ACCESS_FS_IOCTL_DEV right should have no effect on the use of
named UNIX domain sockets.
Suggested-by: Mickaël Salaün <mic@digikod.net>
Signed-off-by: Günther Noack <gnoack@google.com>
Link: https://lore.kernel.org/r/20240419161122.2023765-7-gnoack@google.com
[mic: Add missing stddef.h for offsetof()]
Signed-off-by: Mickaël Salaün <mic@digikod.net>

tools/testing/selftests/landlock/fs_test.c

@@ -14,6 +14,7 @@
 #include <linux/landlock.h>
 #include <linux/magic.h>
 #include <sched.h>
+#include <stddef.h>
 #include <stdio.h>
 #include <string.h>
 #include <sys/capability.h>
@@ -21,8 +22,10 @@
 #include <sys/mount.h>
 #include <sys/prctl.h>
 #include <sys/sendfile.h>
+#include <sys/socket.h>
 #include <sys/stat.h>
 #include <sys/sysmacros.h>
+#include <sys/un.h>
 #include <sys/vfs.h>
 #include <unistd.h>
 
@@ -3985,6 +3988,56 @@ TEST_F_FORK(layout1, named_pipe_ioctl)
 	ASSERT_EQ(child_pid, waitpid(child_pid, NULL, 0));
 }
 
+/* For named UNIX domain sockets, no IOCTL restrictions apply. */
+TEST_F_FORK(layout1, named_unix_domain_socket_ioctl)
+{
+	const char *const path = file1_s1d1;
+	int srv_fd, cli_fd, ruleset_fd;
+	socklen_t size;
+	struct sockaddr_un srv_un, cli_un;
+	const struct landlock_ruleset_attr attr = {
+		.handled_access_fs = LANDLOCK_ACCESS_FS_IOCTL_DEV,
+	};
+
+	/* Sets up a server */
+	srv_un.sun_family = AF_UNIX;
+	strncpy(srv_un.sun_path, path, sizeof(srv_un.sun_path));
+
+	ASSERT_EQ(0, unlink(path));
+	srv_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LE(0, srv_fd);
+
+	size = offsetof(struct sockaddr_un, sun_path) + strlen(srv_un.sun_path);
+	ASSERT_EQ(0, bind(srv_fd, (struct sockaddr *)&srv_un, size));
+	ASSERT_EQ(0, listen(srv_fd, 10 /* qlen */));
+
+	/* 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));
+
+	/* Sets up a client connection to it */
+	cli_un.sun_family = AF_UNIX;
+	cli_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+	ASSERT_LE(0, cli_fd);
+
+	size = offsetof(struct sockaddr_un, sun_path) + strlen(cli_un.sun_path);
+	ASSERT_EQ(0, bind(cli_fd, (struct sockaddr *)&cli_un, size));
+
+	bzero(&cli_un, sizeof(cli_un));
+	cli_un.sun_family = AF_UNIX;
+	strncpy(cli_un.sun_path, path, sizeof(cli_un.sun_path));
+	size = offsetof(struct sockaddr_un, sun_path) + strlen(cli_un.sun_path);
+
+	ASSERT_EQ(0, connect(cli_fd, (struct sockaddr *)&cli_un, size));
+
+	/* FIONREAD and other IOCTLs should not be forbidden. */
+	EXPECT_EQ(0, test_fionread_ioctl(cli_fd));
+
+	ASSERT_EQ(0, close(cli_fd));
+}
+
 /* clang-format off */
 FIXTURE(ioctl) {};