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[net-next,1/8] macvtap: fix a possible race between queue selection and changing queues

Message ID 1370512480-14272-2-git-send-email-jasowang@redhat.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Jason Wang June 6, 2013, 9:54 a.m. UTC 
Complier may generate codes that re-read the vlan->numvtaps during
macvtap_get_queue(). This may lead a race if vlan->numvtaps were changed in the
same time and which 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 vlan->numvtaps were only read once.

Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/macvtap.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
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Patch

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 68efb91..5e485e3 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -172,7 +172,7 @@  static struct macvtap_queue *macvtap_get_queue(struct net_device *dev,
 {
 	struct macvlan_dev *vlan = netdev_priv(dev);
 	struct macvtap_queue *tap = NULL;
-	int numvtaps = vlan->numvtaps;
+	int numvtaps = ACCESS_ONCE(vlan->numvtaps);
 	__u32 rxq;
 
 	if (!numvtaps)