Messages in this thread | | | Date | Wed, 5 Jun 2013 13:33:32 +0300 | From | "Michael S. Tsirkin" <> | Subject | Re: [PATCH] tuntap: fix a possible race between queue selection and changing queues |
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On Wed, Jun 05, 2013 at 04:44:57PM +0800, Jason Wang wrote: > 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 c8d68e6be1c3b242f1c598595830890b65cea64a > (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>
This is a theoretical problem, right? So no need for stable.
> --- > drivers/net/tun.c | 2 +- > 1 files changed, 1 insertions(+), 1 deletions(-) > > diff --git a/drivers/net/tun.c b/drivers/net/tun.c > index f042b03..adfcde7 100644 > --- a/drivers/net/tun.c > +++ b/drivers/net/tun.c > @@ -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) { > -- > 1.7.1
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