netdev - [RFC 1/4] iosm: fix stats and RCU bugs in RX

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Message-Id: <20210601100320.48d067d87f3e.I53608f5de5828db7066d29e5774bcf8a19e0f642@changeid>
Date:   Tue,  1 Jun 2021 10:05:35 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     linux-wireless@...r.kernel.org, netdev@...r.kernel.org
Cc:     m.chetan.kumar@...el.com, loic.poulain@...aro.org,
        Johannes Berg <johannes.berg@...el.com>
Subject: [RFC 1/4] iosm: fix stats and RCU bugs in RX

From: Johannes Berg <johannes.berg@...el.com>

Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 drivers/net/wwan/iosm/iosm_ipc_wwan.c | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wwan/iosm/iosm_ipc_wwan.c b/drivers/net/wwan/iosm/iosm_ipc_wwan.c
index 02c35bc86674..719c88d9b2e9 100644
--- a/drivers/net/wwan/iosm/iosm_ipc_wwan.c
+++ b/drivers/net/wwan/iosm/iosm_ipc_wwan.c
@@ -312,7 +312,8 @@ int ipc_wwan_receive(struct iosm_wwan *ipc_wwan, struct sk_buff *skb_arg,
 		     bool dss, int if_id)
 {
 	struct sk_buff *skb = skb_arg;
-	struct net_device_stats stats;
+	struct net_device_stats *stats;
+	struct iosm_net_link *priv;
 	int ret;
 
 	if ((skb->data[0] & IOSM_IP_TYPE_MASK) == IOSM_IP_TYPE_IPV4)
@@ -325,19 +326,27 @@ int ipc_wwan_receive(struct iosm_wwan *ipc_wwan, struct sk_buff *skb_arg,
 
 	if (if_id < (IP_MUX_SESSION_START - 1) ||
 	    if_id > (IP_MUX_SESSION_END - 1)) {
-		dev_kfree_skb(skb);
-		return -EINVAL;
+		ret = -EINVAL;
+		goto free;
 	}
 
 	rcu_read_lock();
-	skb->dev = rcu_dereference(ipc_wwan->sub_netlist[if_id])->netdev;
-	stats = rcu_dereference(ipc_wwan->sub_netlist[if_id])->netdev->stats;
-	stats.rx_packets++;
-	stats.rx_bytes += skb->len;
+	priv = rcu_dereference(ipc_wwan->sub_netlist[if_id]);
+	if (!priv) {
+		ret = -EINVAL;
+		goto unlock;
+	}
+	skb->dev = priv->netdev;
+	stats = &priv->netdev->stats;
+	stats->rx_packets++;
+	stats->rx_bytes += skb->len;
 
 	ret = netif_rx(skb);
+	skb = NULL;
+unlock:
 	rcu_read_unlock();
-
+free:
+	dev_kfree_skb(skb);
 	return ret;
 }
 
-- 
2.31.1