[NET]: Make device event notification network namespace safe

Every user of the network device notifiers is either a protocol
stack or a pseudo device.  If a protocol stack that does not have
support for multiple network namespaces receives an event for a
device that is not in the initial network namespace it quite possibly
can get confused and do the wrong thing.

To avoid problems until all of the protocol stacks are converted
this patch modifies all netdev event handlers to ignore events on
devices that are not in the initial network namespace.

As the rest of the code is made network namespace aware these
checks can be removed.

Signed-off-by: Eric W. Biederman <ebiederm@xmission.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 0 deletions

diff --git a/net/ipv4/arp.c b/net/ipv4/arp.c
index bde129708e2..a11e7a5c1da 100644
--- a/net/ipv4/arp.c
+++ b/net/ipv4/arp.c
@@ -1205,6 +1205,9 @@ static int arp_netdev_event(struct notifier_block *this, unsigned long event, vo
 {
         struct net_device *dev = ptr;
 
+        if (dev->nd_net != &init_net)
+                return NOTIFY_DONE;
+
         switch (event) {
         case NETDEV_CHANGEADDR:
                 neigh_changeaddr(&arp_tbl, dev);