From 92bb73ea2c434618a68a58a2f3a5c3fd0b660d18 Mon Sep 17 00:00:00 2001
From: Jason Wang <jasowang@redhat.com>
Date: Wed, 5 Jun 2013 16:44:57 +0800
Subject: [PATCH] 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 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>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
drivers/net/tun.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 89776c5921518..b1cbfbcff789c 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) {
--
2.30.2