macvlan: fix failure during registration v3

If macvlan_common_newlink fails in register_netdevice after macvlan_init
then it decrements port->count twice, first in macvlan_uninit (from
register_netdevice or rollback_registered) and then again in
macvlan_common_newlink.
A similar problem may exist in the ipvlan driver.
This patch consolidates modifications to port->count into macvlan_init
and macvlan_uninit (thanks to Eric Biederman for suggesting this approach).

v3: remove macvtap specific bits.

Signed-off-by: Francesco Ruggeri <fruggeri@arista.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 6 deletions

diff --git a/drivers/net/macvlan.c b/drivers/net/macvlan.c
index 2bcf1f321bea..cb01023eab41 100644
--- a/drivers/net/macvlan.c
+++ b/drivers/net/macvlan.c
@@ -795,6 +795,7 @@ static int macvlan_init(struct net_device *dev)
 {
         struct macvlan_dev *vlan = netdev_priv(dev);
         const struct net_device *lowerdev = vlan->lowerdev;
+        struct macvlan_port *port = vlan->port;
 
         dev->state              = (dev->state & ~MACVLAN_STATE_MASK) |
                                   (lowerdev->state & MACVLAN_STATE_MASK);
@@ -812,6 +813,8 @@ static int macvlan_init(struct net_device *dev)
         if (!vlan->pcpu_stats)
                 return -ENOMEM;
 
+        port->count += 1;
+
         return 0;
 }
 
@@ -1312,10 +1315,9 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
                         return err;
         }
 
-        port->count += 1;
         err = register_netdevice(dev);
         if (err < 0)
-                goto destroy_port;
+                return err;
 
         dev->priv_flags |= IFF_MACVLAN;
         err = netdev_upper_dev_link(lowerdev, dev);
@@ -1330,10 +1332,6 @@ int macvlan_common_newlink(struct net *src_net, struct net_device *dev,
 
 unregister_netdev:
         unregister_netdevice(dev);
-destroy_port:
-        port->count -= 1;
-        if (!port->count)
-                macvlan_port_destroy(lowerdev);
 
         return err;
 }