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authorJason Wang <jasowang@redhat.com>2019-05-08 23:20:18 -0400
committerDavid S. Miller <davem@davemloft.net>2019-05-09 09:21:42 -0700
commit9871a9e47a2646fe30ae7fd2e67668a8d30912f6 (patch)
tree06772218a11b4c05b06d31ed92c649cac61b6a8b /drivers/net
parenttuntap: fix dividing by zero in ebpf queue selection (diff)
downloadlinux-dev-9871a9e47a2646fe30ae7fd2e67668a8d30912f6.tar.xz
linux-dev-9871a9e47a2646fe30ae7fd2e67668a8d30912f6.zip
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: c8d68e6be1c3b ("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>
Diffstat (limited to '')
-rw-r--r--drivers/net/tun.c7
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a52bd47e7aa2..abae165dcca5 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -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++) {