rtnetlink: do not depend on RTNL for IFLA_TXQLEN output

rtnl_fill_ifinfo() can read dev->tx_queue_len locklessly,
granted we add corresponding READ_ONCE()/WRITE_ONCE() annotations.

Add missing READ_ONCE(dev->tx_queue_len) in teql_enqueue()
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

net/core/dev.c

@@ -8959,7 +8959,7 @@ int dev_change_tx_queue_len(struct net_device *dev, unsigned long new_len)
 		return -ERANGE;
 
 	if (new_len != orig_len) {
-		dev->tx_queue_len = new_len;
+		WRITE_ONCE(dev->tx_queue_len, new_len);
 		res = call_netdevice_notifiers(NETDEV_CHANGE_TX_QUEUE_LEN, dev);
 		res = notifier_to_errno(res);
 		if (res)
@@ -8973,7 +8973,7 @@ int dev_change_tx_queue_len(struct net_device *dev, unsigned long new_len)
 
 err_rollback:
 	netdev_err(dev, "refused to change device tx_queue_len\n");
-	dev->tx_queue_len = orig_len;
+	WRITE_ONCE(dev->tx_queue_len, orig_len);
 	return res;
 }
 

net/core/rtnetlink.c

@@ -1837,7 +1837,7 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 	if (nla_put_string(skb, IFLA_IFNAME, devname))
 		goto nla_put_failure;
 
-	if (nla_put_u32(skb, IFLA_TXQLEN, dev->tx_queue_len) ||
+	if (nla_put_u32(skb, IFLA_TXQLEN, READ_ONCE(dev->tx_queue_len)) ||
 	    nla_put_u8(skb, IFLA_OPERSTATE,
 		       netif_running(dev) ? dev->operstate : IF_OPER_DOWN) ||
 	    nla_put_u8(skb, IFLA_LINKMODE, dev->link_mode) ||

net/sched/sch_api.c

@@ -1334,7 +1334,7 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 	 * before again attaching a qdisc.
 	 */
 	if ((dev->priv_flags & IFF_NO_QUEUE) && (dev->tx_queue_len == 0)) {
-		dev->tx_queue_len = DEFAULT_TX_QUEUE_LEN;
+		WRITE_ONCE(dev->tx_queue_len, DEFAULT_TX_QUEUE_LEN);
 		netdev_info(dev, "Caught tx_queue_len zero misconfig\n");
 	}
 

net/sched/sch_teql.c

@@ -78,7 +78,7 @@ teql_enqueue(struct sk_buff *skb, struct Qdisc *sch, struct sk_buff **to_free)
 	struct net_device *dev = qdisc_dev(sch);
 	struct teql_sched_data *q = qdisc_priv(sch);
 
-	if (q->q.qlen < dev->tx_queue_len) {
+	if (q->q.qlen < READ_ONCE(dev->tx_queue_len)) {
 		__skb_queue_tail(&q->q, skb);
 		return NET_XMIT_SUCCESS;
 	}