ipv4: arp_notify address list bug

This fixes a bug with arp_notify.

If arp_notify is enabled, kernel will crash if address is changed
and no IP address is assigned.
  http://bugzilla.kernel.org/show_bug.cgi?id=14330

Reported-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index e92f1fd..5df2f6a 100644 (file)
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1077,12 +1077,16 @@ static int inetdev_event(struct notifier_block *this, unsigned long event,
                ip_mc_up(in_dev);
                /* fall through */
        case NETDEV_CHANGEADDR:
-               if (IN_DEV_ARP_NOTIFY(in_dev))
-                       arp_send(ARPOP_REQUEST, ETH_P_ARP,
-                                in_dev->ifa_list->ifa_address,
-                                dev,
-                                in_dev->ifa_list->ifa_address,
-                                NULL, dev->dev_addr, NULL);
+               /* Send gratuitous ARP to notify of link change */
+               if (IN_DEV_ARP_NOTIFY(in_dev)) {
+                       struct in_ifaddr *ifa = in_dev->ifa_list;
+
+                       if (ifa)
+                               arp_send(ARPOP_REQUEST, ETH_P_ARP,
+                                        ifa->ifa_address, dev,
+                                        ifa->ifa_address, NULL,
+                                        dev->dev_addr, NULL);
+               }
                break;
        case NETDEV_DOWN:
                ip_mc_down(in_dev);