From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: [PATCH] tuntap: fix a possible race between queue selection and changing queues Date: Wed, 5 Jun 2013 16:44:57 +0800 Message-ID: <1370421897-30933-1-git-send-email-jasowang@redhat.com> Cc: Jason Wang To: davem@davemloft.net, mst@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org Return-path: Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org 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 Cc: Michael S. Tsirkin Signed-off-by: Jason Wang --- 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