net: qualcomm: rmnet: don't over-count statistics

stable inclusion
from stable-5.10.46
commit 0e185a7b285d2a84341a9d29ac935408ac5b662d
bugzilla: 168323
CVE: NA

--------------------------------

[ Upstream commit 994c393b ]

The purpose of the loop using u64_stats_fetch_*_irq() is to ensure
statistics on a given CPU are collected atomically. If one of the
statistics values gets updated within the begin/retry window, the
loop will run again.

Currently the statistics totals are updated inside that window.
This means that if the loop ever retries, the statistics for the
CPU will be counted more than once.

Fix this by taking a snapshot of a CPU's statistics inside the
protected window, and then updating the counters with the snapshot
values after exiting the loop.

(Also add a newline at the end of this file...)

Fixes: 192c4b5d ("net: qualcomm: rmnet: Add support for 64 bit stats")
Signed-off-by: NAlex Elder <elder@linaro.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Signed-off-by: NSasha Levin <sashal@kernel.org>
Signed-off-by: NChen Jun <chenjun102@huawei.com>
Acked-by: NWeilong Chen <chenweilong@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

drivers/net/ethernet/qualcomm/rmnet/rmnet_vnd.c

@@ -125,24 +125,24 @@ static void rmnet_get_stats64(struct net_device *dev,
 			      struct rtnl_link_stats64 *s)
 {
 	struct rmnet_priv *priv = netdev_priv(dev);
-	struct rmnet_vnd_stats total_stats;
+	struct rmnet_vnd_stats total_stats = { };
 	struct rmnet_pcpu_stats *pcpu_ptr;
+	struct rmnet_vnd_stats snapshot;
 	unsigned int cpu, start;
 
-	memset(&total_stats, 0, sizeof(struct rmnet_vnd_stats));
-
 	for_each_possible_cpu(cpu) {
 		pcpu_ptr = per_cpu_ptr(priv->pcpu_stats, cpu);
 
 		do {
 			start = u64_stats_fetch_begin_irq(&pcpu_ptr->syncp);
-			total_stats.rx_pkts += pcpu_ptr->stats.rx_pkts;
-			total_stats.rx_bytes += pcpu_ptr->stats.rx_bytes;
-			total_stats.tx_pkts += pcpu_ptr->stats.tx_pkts;
-			total_stats.tx_bytes += pcpu_ptr->stats.tx_bytes;
+			snapshot = pcpu_ptr->stats;	/* struct assignment */
 		} while (u64_stats_fetch_retry_irq(&pcpu_ptr->syncp, start));
 
-		total_stats.tx_drops += pcpu_ptr->stats.tx_drops;
+		total_stats.rx_pkts += snapshot.rx_pkts;
+		total_stats.rx_bytes += snapshot.rx_bytes;
+		total_stats.tx_pkts += snapshot.tx_pkts;
+		total_stats.tx_bytes += snapshot.tx_bytes;
+		total_stats.tx_drops += snapshot.tx_drops;
 	}
 
 	s->rx_packets = total_stats.rx_pkts;
@@ -353,4 +353,4 @@ int rmnet_vnd_update_dev_mtu(struct rmnet_port *port,
 	}
 
 	return 0;
-}
\ No newline at end of file
+}