net: Fix userspace RTM_NEWLINK notifications.

I received some bug reports about userspace programs having problems
because after RTM_NEWLINK was received they could not immediate access
files under /proc/sys/net/ because they had not been registered yet.

The original problem was trivially fixed by moving the userspace
notification from rtnetlink_event() to the end of
register_netdevice().

When testing that change I discovered I was still getting RTM_NEWLINK
events before I could access proc and I was also getting RTM_NEWLINK
events after I was seeing RTM_DELLINK.  Things practically guaranteed
to confuse userspace.

After a little more investigation these extra notifications proved to
be from the new notifiers NETDEV_POST_INIT and NETDEV_UNREGISTER_BATCH
hitting the default case in rtnetlink_event, and triggering
unnecessary RTM_NEWLINK messages.

rtnetlink_event now explicitly handles NETDEV_UNREGISTER_BATCH and
NETDEV_POST_INIT to avoid sending the incorrect userspace
notifications.

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

diff --git a/net/core/dev.c b/net/core/dev.c
index 6fe7d73..be9924f 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -5035,6 +5035,11 @@ int register_netdevice(struct net_device *dev)
                rollback_registered(dev);
                dev->reg_state = NETREG_UNREGISTERED;
        }
+       /*
+        *      Prevent userspace races by waiting until the network
+        *      device is fully setup before sending notifications.
+        */
+       rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
 
 out:
        return ret;
@@ -5597,6 +5602,12 @@ int dev_change_net_namespace(struct net_device *dev, struct net *net, const char
        /* Notify protocols, that a new device appeared. */
        call_netdevice_notifiers(NETDEV_REGISTER, dev);
 
+       /*
+        *      Prevent userspace races by waiting until the network
+        *      device is fully setup before sending notifications.
+        */
+       rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
+
        synchronize_net();
        err = 0;
 out:

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 33148a5..794bcb8 100644 (file)
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -1364,15 +1364,15 @@ static int rtnetlink_event(struct notifier_block *this, unsigned long event, voi
        case NETDEV_UNREGISTER:
                rtmsg_ifinfo(RTM_DELLINK, dev, ~0U);
                break;
-       case NETDEV_REGISTER:
-               rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
-               break;
        case NETDEV_UP:
        case NETDEV_DOWN:
                rtmsg_ifinfo(RTM_NEWLINK, dev, IFF_UP|IFF_RUNNING);
                break;
+       case NETDEV_POST_INIT:
+       case NETDEV_REGISTER:
        case NETDEV_CHANGE:
        case NETDEV_GOING_DOWN:
+       case NETDEV_UNREGISTER_BATCH:
                break;
        default:
                rtmsg_ifinfo(RTM_NEWLINK, dev, 0);