[PATCH next] ipvlan: Fix failure path in dev registration during link creation

[Mahesh Bandewar]

From: Mahesh Bandewar <mahe...@google.com>

When newlink creation fails at device-registration, the port->count
is decremented twice. Francesco Ruggeri (frugg...@arista.com) found
this issue in Macvlan and the same exists in IPvlan driver too.

While fixing this issue I noticed another issue of missing unregister
in case of failure, so adding it to the fix which is similar to the
macvlan fix by Francesco in SHA1:308379607548524b8d86dbf20134681024935e0b

Reported-by: Francesco Ruggeri <frugg...@arista.com>
Signed-off-by: Mahesh Bandewar <mahe...@google.com>
CC: Eric Dumazet <eduma...@google.com>
CC: Eric W. Biederman <ebied...@xmission.com>
---
 drivers/net/ipvlan/ipvlan_main.c | 19 ++++++++-----------
 1 file changed, 8 insertions(+), 11 deletions(-)

diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index 57941d3f4227..1c4d395fbd49 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -113,6 +113,7 @@ static int ipvlan_init(struct net_device *dev)
 {
        struct ipvl_dev *ipvlan = netdev_priv(dev);
        const struct net_device *phy_dev = ipvlan->phy_dev;
+       struct ipvl_port *port = ipvlan->port;
 
        dev->state = (dev->state & ~IPVLAN_STATE_MASK) |
                     (phy_dev->state & IPVLAN_STATE_MASK);
@@ -128,6 +129,8 @@ static int ipvlan_init(struct net_device *dev)
        if (!ipvlan->pcpu_stats)
                return -ENOMEM;
 
+       port->count += 1;
+
        return 0;
 }
 
@@ -481,27 +484,21 @@ static int ipvlan_link_new(struct net *src_net, struct 
net_device *dev,
 
        dev->priv_flags |= IFF_IPVLAN_SLAVE;
 
-       port->count += 1;
        err = register_netdevice(dev);
        if (err < 0)
-               goto ipvlan_destroy_port;
+               return err;
 
        err = netdev_upper_dev_link(phy_dev, dev);
-       if (err)
-               goto ipvlan_destroy_port;
+       if (err) {
+               unregister_netdevice(dev);
+               return err;
+       }
 
        list_add_tail_rcu(&ipvlan->pnode, &port->ipvlans);
        ipvlan_set_port_mode(port, mode);
 
        netif_stacked_transfer_operstate(phy_dev, dev);
        return 0;
-
-ipvlan_destroy_port:
-       port->count -= 1;
-       if (!port->count)
-               ipvlan_port_destroy(phy_dev);
-
-       return err;
 }
 
 static void ipvlan_link_delete(struct net_device *dev, struct list_head *head)
-- 
2.8.0.rc3.226.g39d4020