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tuntap: fix a possible race between queue selection and changing queues

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Complier may generate codes that re-read the tun->numqueues during
tun_select_queue(). This may be a race if vlan->numqueues were changed in the
same time and can lead unexpected result (e.g. very huge value).

We need prevent the compiler from generating such codes by adding an
ACCESS_ONCE() to make sure tun->numqueues were only read once.

Bug were introduced by commit c8d68e6be1
(tuntap: multiqueue support).

Reported-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jason Wang 2013-06-05 16:44:57 +08:00 committed by David S. Miller
parent 4364d5f96e
commit 92bb73ea2c
1 changed files with 1 additions and 1 deletions
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2
drivers/net/tun.c
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@ -352,7 +352,7 @@ static u16 tun_select_queue(struct net_device *dev, struct sk_buff *skb)
u32 numqueues = 0;
rcu_read_lock();
numqueues = tun->numqueues;
numqueues = ACCESS_ONCE(tun->numqueues);
txq = skb_get_rxhash(skb);
if (txq) {