selinux: skip bounded transition processing if the policy isn't loaded

We can't do anything reasonable in security_bounded_transition() if we
don't have a policy loaded, and in fact we could run into problems
with some of the code inside expecting a policy.  Fix these problems
like we do many others in security/selinux/ss/services.c by checking
to see if the policy is loaded (ss_initialized) and returning quickly
if it isn't.

Reported-by: syzbot <syzkaller-bugs@googlegroups.com>
Signed-off-by: Paul Moore <paul@paul-moore.com>
Acked-by: Stephen Smalley <sds@tycho.nsa.gov>
Reviewed-by: James Morris <james.l.morris@oracle.com>

security/selinux/ss/services.c

@@ -867,6 +867,9 @@ int security_bounded_transition(u32 old_sid, u32 new_sid)
 	int index;
 	int rc;
 
+	if (!ss_initialized)
+		return 0;
+
 	read_lock(&policy_rwlock);
 
 	rc = -EINVAL;