[PATCH net] net: hns3: fix data race in hns3_fetch_stats

[David Yang <mmyangfl@gmail.com>]

In hns3_fetch_stats(), ring statistics, protected by u64_stats_sync, are
read and accumulated in ignorance of possible u64_stats_fetch_retry()
events. These statistics are already accumulated by
hns3_ring_stats_update(). Fix this by reading them into a temporary
buffer first.

Fixes: b20d7fe51e0d ("net: hns3: add some statitics info to tx process")
Signed-off-by: David Yang <mmyangfl@gmail.com>
---
 .../net/ethernet/hisilicon/hns3/hns3_enet.c   | 69 ++++++++++---------
 1 file changed, 36 insertions(+), 33 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index 7b9269f6fdfc..a47464a22751 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -2530,44 +2530,47 @@ static netdev_features_t hns3_features_check(struct sk_buff *skb,
 static void hns3_fetch_stats(struct rtnl_link_stats64 *stats,
 			     struct hns3_enet_ring *ring, bool is_tx)
 {
+	struct ring_stats ring_stats;
 	unsigned int start;
 
 	do {
 		start = u64_stats_fetch_begin(&ring->syncp);
-		if (is_tx) {
-			stats->tx_bytes += ring->stats.tx_bytes;
-			stats->tx_packets += ring->stats.tx_pkts;
-			stats->tx_dropped += ring->stats.sw_err_cnt;
-			stats->tx_dropped += ring->stats.tx_vlan_err;
-			stats->tx_dropped += ring->stats.tx_l4_proto_err;
-			stats->tx_dropped += ring->stats.tx_l2l3l4_err;
-			stats->tx_dropped += ring->stats.tx_tso_err;
-			stats->tx_dropped += ring->stats.over_max_recursion;
-			stats->tx_dropped += ring->stats.hw_limitation;
-			stats->tx_dropped += ring->stats.copy_bits_err;
-			stats->tx_dropped += ring->stats.skb2sgl_err;
-			stats->tx_dropped += ring->stats.map_sg_err;
-			stats->tx_errors += ring->stats.sw_err_cnt;
-			stats->tx_errors += ring->stats.tx_vlan_err;
-			stats->tx_errors += ring->stats.tx_l4_proto_err;
-			stats->tx_errors += ring->stats.tx_l2l3l4_err;
-			stats->tx_errors += ring->stats.tx_tso_err;
-			stats->tx_errors += ring->stats.over_max_recursion;
-			stats->tx_errors += ring->stats.hw_limitation;
-			stats->tx_errors += ring->stats.copy_bits_err;
-			stats->tx_errors += ring->stats.skb2sgl_err;
-			stats->tx_errors += ring->stats.map_sg_err;
-		} else {
-			stats->rx_bytes += ring->stats.rx_bytes;
-			stats->rx_packets += ring->stats.rx_pkts;
-			stats->rx_dropped += ring->stats.l2_err;
-			stats->rx_errors += ring->stats.l2_err;
-			stats->rx_errors += ring->stats.l3l4_csum_err;
-			stats->rx_crc_errors += ring->stats.l2_err;
-			stats->multicast += ring->stats.rx_multicast;
-			stats->rx_length_errors += ring->stats.err_pkt_len;
-		}
+		ring_stats = ring->stats;
 	} while (u64_stats_fetch_retry(&ring->syncp, start));
+
+	if (is_tx) {
+		stats->tx_bytes += ring_stats.tx_bytes;
+		stats->tx_packets += ring_stats.tx_pkts;
+		stats->tx_dropped += ring_stats.sw_err_cnt;
+		stats->tx_dropped += ring_stats.tx_vlan_err;
+		stats->tx_dropped += ring_stats.tx_l4_proto_err;
+		stats->tx_dropped += ring_stats.tx_l2l3l4_err;
+		stats->tx_dropped += ring_stats.tx_tso_err;
+		stats->tx_dropped += ring_stats.over_max_recursion;
+		stats->tx_dropped += ring_stats.hw_limitation;
+		stats->tx_dropped += ring_stats.copy_bits_err;
+		stats->tx_dropped += ring_stats.skb2sgl_err;
+		stats->tx_dropped += ring_stats.map_sg_err;
+		stats->tx_errors += ring_stats.sw_err_cnt;
+		stats->tx_errors += ring_stats.tx_vlan_err;
+		stats->tx_errors += ring_stats.tx_l4_proto_err;
+		stats->tx_errors += ring_stats.tx_l2l3l4_err;
+		stats->tx_errors += ring_stats.tx_tso_err;
+		stats->tx_errors += ring_stats.over_max_recursion;
+		stats->tx_errors += ring_stats.hw_limitation;
+		stats->tx_errors += ring_stats.copy_bits_err;
+		stats->tx_errors += ring_stats.skb2sgl_err;
+		stats->tx_errors += ring_stats.map_sg_err;
+	} else {
+		stats->rx_bytes += ring_stats.rx_bytes;
+		stats->rx_packets += ring_stats.rx_pkts;
+		stats->rx_dropped += ring_stats.l2_err;
+		stats->rx_errors += ring_stats.l2_err;
+		stats->rx_errors += ring_stats.l3l4_csum_err;
+		stats->rx_crc_errors += ring_stats.l2_err;
+		stats->multicast += ring_stats.rx_multicast;
+		stats->rx_length_errors += ring_stats.err_pkt_len;
+	}
 }
 
 static void hns3_nic_get_stats64(struct net_device *netdev,
-- 
2.51.0