landlock: Use square brackets around "landlock-ruleset"

Make the name of the anon inode fd "[landlock-ruleset]" instead of
"landlock-ruleset". This is minor but most anon inode fds already
carry square brackets around their name:

    [eventfd]
    [eventpoll]
    [fanotify]
    [fscontext]
    [io_uring]
    [pidfd]
    [signalfd]
    [timerfd]
    [userfaultfd]

For the sake of consistency lets do the same for the landlock-ruleset anon
inode fd that comes with landlock. We did the same in
1cdc415 ("uapi, fsopen: use square brackets around "fscontext" [ver #2]")
for the new mount api.

Cc: linux-security-module@vger.kernel.org
Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Link: https://lore.kernel.org/r/20211011133704.1704369-1-brauner@kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Mickaël Salaün <mic@linux.microsoft.com>

Author: Christian Brauner

security/landlock/syscalls.c

@@ -192,7 +192,7 @@ SYSCALL_DEFINE3(landlock_create_ruleset,
 		return PTR_ERR(ruleset);
 
 	/* Creates anonymous FD referring to the ruleset. */
-	ruleset_fd = anon_inode_getfd("landlock-ruleset", &ruleset_fops,
+	ruleset_fd = anon_inode_getfd("[landlock-ruleset]", &ruleset_fops,
 			ruleset, O_RDWR | O_CLOEXEC);
 	if (ruleset_fd < 0)
 		landlock_put_ruleset(ruleset);