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Commit 17d8a9eb authored by Jason Wang's avatar Jason Wang Committed by Greg Kroah-Hartman
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tuntap: synchronize through tfiles array instead of tun->numqueues 



[ Upstream commit 9871a9e47a2646fe30ae7fd2e67668a8d30912f6 ]

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: c8d68e6b ("tuntap: multiqueue support")
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Reviewed-by: default avatarWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 9c79732f

drivers/net/tun.c

+6 −1
Original line number Diff line number Diff line
@@ -708,6 +708,8 @@ 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) {
@@ -1090,7 +1092,7 @@ 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))
@@ -1281,6 +1283,7 @@ 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();
@@ -1289,6 +1292,8 @@ 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++) {