UBUNTU: SAUCE: apparmor: Disallow update of cred when then subjective != the objective cred

BugLink: http://bugs.launchpad.net/bugs/1430546Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

security/apparmor/context.c

@@ -100,6 +100,9 @@ int aa_replace_current_label(struct aa_label *label)
 	if (cxt->label == label)
 		return 0;
 
+	if (current_cred() != current_real_cred())
+		return -EBUSY;
+
 	new  = prepare_creds();
 	if (!new)
 		return -ENOMEM;