UBUNTU: SAUCE: apparmor: Fix: insert race between label_update and label_merge

BugLink: http://bugs.launchpad.net/bugs/1448912

it is possible for a label_merge to be racing label_update resulting
in the AA_BUG(__aa_label_remove_and_insert()) to trip. Instead check
if a version of label has already been inserted and gracefully fail
if label_update lost the race.
Signed-off-by: John Johansen <john.johansen@canonical.com>
Signed-off-by: Tim Gardner <tim.gardner@canonical.com>

security/apparmor/label.c

@@ -1782,15 +1782,22 @@ static struct aa_label *__label_update(struct aa_label *label)
 	if (invcount) {
 		l->size -= aa_sort_and_merge_profiles(l->size, &l->ent[0]);
 		if (labels_set(label) == labels_set(l)) {
-			AA_BUG(__aa_label_remove_and_insert(labels_set(label), label, l) != l);
+			goto insert;
 		} else {
 			aa_label_remove(labels_set(label), label);
 			goto other_ls_insert;
 		}
 	} else {
 		AA_BUG(labels_ns(label) != labels_ns(l));
-		AA_BUG(__aa_label_remove_and_insert(labels_set(label), label, l) != l);
+		goto insert;
 	}
+insert:
+	tmp = __aa_label_remove_and_insert(labels_set(label), label, l);
+	if (tmp != l) {
+		aa_get_label(tmp);
+		aa_label_free(l);
+	 }
+
 	write_unlock_irqrestore(&ls->lock, flags);
 
 	return l;