Commit 9871a9e4 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

tuntap: synchronize through tfiles array instead of tun->numqueues

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>
parent a35d310f
......@@ -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++) {
......
Supports Markdown
0% or .
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment