Commit 92bb73ea authored Jun 05, 2013 by Jason Wang Committed by David S. Miller Jun 10, 2013

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



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 c8d68e6b
(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>

parent 4364d5f9

drivers/net/tun.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -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) {

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