tuntap: synchronize through tfiles array instead of tun->numqueues (9871a9e4) · Commits · 戴 / test

When a queue(tfile) is detached through __tun_detach(), we move the last enabled tfile to the position where detached one sit but don't NULL out last position. We expect to synchronize the datapath through tun->numqueues. Unfortunately, this won't work since we're lacking sufficient mechanism to order or synchronize the access to tun->numqueues. To fix this, NULL out the last position during detaching and check RCU protected tfile against NULL instead of checking tun->numqueues in datapath. Cc: YueHaibing <yuehaibing@huawei.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Cc: weiyongjun (A) <weiyongjun1@huawei.com> Cc: Eric Dumazet <eric.dumazet@gmail.com> Fixes: ("tuntap: multiqueue support") Signed-off-by:

Jason Wang <jasowang@redhat.com> Reviewed-by:

Wei Yongjun <weiyongjun1@huawei.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

drivers/net/tun.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -704,6 +704,8 @@ static void __tun_detach(struct tun_file *tfile, bool clean)
		tun->tfiles[tun->numqueues - 1]);
		ntfile = rtnl_dereference(tun->tfiles[index]);
		ntfile->queue_index = index;
		rcu_assign_pointer(tun->tfiles[tun->numqueues - 1],
		NULL);

		--tun->numqueues;
		if (clean) {
		@@ -1086,7 +1088,7 @@ static netdev_tx_t tun_net_xmit(struct sk_buff skb, struct net_device dev)
		tfile = rcu_dereference(tun->tfiles[txq]);

		/* Drop packet if interface is not attached */
		if (txq >= tun->numqueues)
		if (!tfile)
		goto drop;

		if (!rcu_dereference(tun->steering_prog))
		@@ -1309,6 +1311,7 @@ static int tun_xdp_xmit(struct net_device *dev, int n,

		rcu_read_lock();

		resample:
		numqueues = READ_ONCE(tun->numqueues);
		if (!numqueues) {
		rcu_read_unlock();
		@@ -1317,6 +1320,8 @@ static int tun_xdp_xmit(struct net_device *dev, int n,

		tfile = rcu_dereference(tun->tfiles[smp_processor_id() %
		numqueues]);
		if (unlikely(!tfile))
		goto resample;

		spin_lock(&tfile->tx_ring.producer_lock);
		for (i = 0; i < n; i++) {

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