netdev - [PATCH 1/5] macvtap: Close a race between macvtap_open and macvtap

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Message-ID: <m1sjmnu4cm.fsf@fess.ebiederm.org>
Date:	Thu, 20 Oct 2011 07:26:01 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	David Miller <davem@...emloft.net>
Cc:	<netdev@...r.kernel.org>, Arnd Bergmann <arnd@...d.de>,
	Jason Wang <jasowang@...hat.com>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Ian Campbell <ian.campbell@...rix.com>,
	Shirly Ma <mashirley@...ibm.com>
Subject: [PATCH 1/5] macvtap: Close a race between macvtap_open and macvtap_dellink.


There is a small window in macvtap_open between looking up a
networking device and calling macvtap_set_queue in which
macvtap_del_queues called from macvtap_dellink.   After
calling macvtap_del_queues it is totally incorrect to
allow macvtap_set_queue to proceed so prevent success by
reporting that all of the available queues are in use.

Signed-off-by: Eric W. Biederman <ebiederm@...ssion.com>
---
 drivers/net/macvtap.c |    2 ++
 1 files changed, 2 insertions(+), 0 deletions(-)

diff --git a/drivers/net/macvtap.c b/drivers/net/macvtap.c
index 3da5578..70aa628 100644
--- a/drivers/net/macvtap.c
+++ b/drivers/net/macvtap.c
@@ -231,6 +231,8 @@ static void macvtap_del_queues(struct net_device *dev)
 		}
 	}
 	BUG_ON(vlan->numvtaps != 0);
+	/* guarantee that any future macvtap_set_queue will fail */
+	vlan->numvtaps = MAX_MACVTAP_QUEUES;
 	spin_unlock(&macvtap_lock);
 
 	synchronize_rcu();
-- 
1.7.2.5

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