batman-adv: protect tt request from double deletion

The list_del() calls were changed to list_del_init() to prevent
an accidental double deletion in batadv_tt_req_node_new().
Signed-off-by: Marek Lindner <mareklindner@neomailbox.ch>
Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>

net/batman-adv/translation-table.c

@@ -2196,7 +2196,7 @@ static void batadv_tt_req_list_free(struct batadv_priv *bat_priv)
 	spin_lock_bh(&bat_priv->tt.req_list_lock);
 
 	list_for_each_entry_safe(node, safe, &bat_priv->tt.req_list, list) {
-		list_del(&node->list);
+		list_del_init(&node->list);
 		kfree(node);
 	}
 
@@ -2232,7 +2232,7 @@ static void batadv_tt_req_purge(struct batadv_priv *bat_priv)
 	list_for_each_entry_safe(node, safe, &bat_priv->tt.req_list, list) {
 		if (batadv_has_timed_out(node->issued_at,
 					 BATADV_TT_REQUEST_TIMEOUT)) {
-			list_del(&node->list);
+			list_del_init(&node->list);
 			kfree(node);
 		}
 	}
@@ -2514,7 +2514,8 @@ static int batadv_send_tt_request(struct batadv_priv *bat_priv,
 		batadv_hardif_free_ref(primary_if);
 	if (ret && tt_req_node) {
 		spin_lock_bh(&bat_priv->tt.req_list_lock);
-		list_del(&tt_req_node->list);
+		/* list_del_init() verifies tt_req_node still is in the list */
+		list_del_init(&tt_req_node->list);
 		spin_unlock_bh(&bat_priv->tt.req_list_lock);
 		kfree(tt_req_node);
 	}
@@ -2951,7 +2952,7 @@ static void batadv_handle_tt_response(struct batadv_priv *bat_priv,
 	list_for_each_entry_safe(node, safe, &bat_priv->tt.req_list, list) {
 		if (!batadv_compare_eth(node->addr, resp_src))
 			continue;
-		list_del(&node->list);
+		list_del_init(&node->list);
 		kfree(node);
 	}