net: ethernet: mtk_eth_soc: missing mutex

Patch 2ed37183 ("netfilter: flowtable: separate replace, destroy and
stats to different workqueues") splits the workqueue per event type. Add
a mutex to serialize updates.

Fixes: 502e84e2 ("net: ethernet: mtk_eth_soc: add flow offloading support")
Reported-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_ppe_offload.c

@@ -391,6 +391,8 @@ mtk_flow_offload_stats(struct mtk_eth *eth, struct flow_cls_offload *f)
 	return 0;
 }
 
+static DEFINE_MUTEX(mtk_flow_offload_mutex);
+
 static int
 mtk_eth_setup_tc_block_cb(enum tc_setup_type type, void *type_data, void *cb_priv)
 {
@@ -398,6 +400,7 @@ mtk_eth_setup_tc_block_cb(enum tc_setup_type type, void *type_data, void *cb_pri
 	struct net_device *dev = cb_priv;
 	struct mtk_mac *mac = netdev_priv(dev);
 	struct mtk_eth *eth = mac->hw;
+	int err;
 
 	if (!tc_can_offload(dev))
 		return -EOPNOTSUPP;
@@ -405,18 +408,24 @@ mtk_eth_setup_tc_block_cb(enum tc_setup_type type, void *type_data, void *cb_pri
 	if (type != TC_SETUP_CLSFLOWER)
 		return -EOPNOTSUPP;
 
+	mutex_lock(&mtk_flow_offload_mutex);
 	switch (cls->command) {
 	case FLOW_CLS_REPLACE:
-		return mtk_flow_offload_replace(eth, cls);
+		err = mtk_flow_offload_replace(eth, cls);
+		break;
 	case FLOW_CLS_DESTROY:
-		return mtk_flow_offload_destroy(eth, cls);
+		err = mtk_flow_offload_destroy(eth, cls);
+		break;
 	case FLOW_CLS_STATS:
-		return mtk_flow_offload_stats(eth, cls);
+		err = mtk_flow_offload_stats(eth, cls);
+		break;
 	default:
-		return -EOPNOTSUPP;
+		err = -EOPNOTSUPP;
+		break;
 	}
+	mutex_unlock(&mtk_flow_offload_mutex);
 
-	return 0;
+	return err;
 }
 
 static int