Subject: Re: macvlan: Fix device ref leak when purging bc_queue

From: <[email-masked]>
Date: Thu, 20 Apr 2017 16:09:56 +0000

Hi Herbert,
I agree with this change, but the same purge would be needed for the macvlan_dellink() call also. 
Thanks,
Joe

________________________________________
From: Herbert Xu <[email-masked]>
Sent: Thursday, April 20, 2017 5:55 AM
To: Ghalam, Joe
Cc: [email-masked]; Wichmann, Clifford; [email-masked]
Subject: macvlan: Fix device ref leak when purging bc_queue

When a parent macvlan device is destroyed we end up purging its
broadcast queue without dropping the device reference count on
the packet source device.  This causes the source device to linger.

This patch drops that reference count.

Fixes: 260916dfb48c ("macvlan: Fix potential use-after free for...")
Reported-by: Joe Ghalam <[email-masked]>
Signed-off-by: Herbert Xu <[email-masked]>

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 9261722..b34eaaa 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -1139,6 +1139,7 @@ static int macvlan_port_create(struct net_device *dev)
 static void macvlan_port_destroy(struct net_device *dev)
 {
        struct macvlan_port *port = macvlan_port_get_rtnl(dev);
+       struct sk_buff *skb;

        dev->priv_flags &= ~IFF_MACVLAN_PORT;
        netdev_rx_handler_unregister(dev);
@@ -1147,7 +1148,15 @@ static void macvlan_port_destroy(struct net_device *dev)
         * but we need to cancel it and purge left skbs if any.
         */
        cancel_work_sync(&port->bc_work);
-       __skb_queue_purge(&port->bc_queue);
+
+       while ((skb = __skb_dequeue(&port->bc_queue))) {
+               const struct macvlan_dev *src = MACVLAN_SKB_CB(skb)->src;
+
+               if (src)
+                       dev_put(src->dev);
+
+               kfree_skb(skb);
+       }

        kfree(port);
 }
--
Email: Herbert Xu <[email-masked]>
Home Page: http://gondor.apana.org.au/~herbert/
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