netdev - [PATCH] ipv4: arp_notify address list bug

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Message-ID: <4ACAD393.5080909@gmail.com>
Date:	Tue, 06 Oct 2009 07:20:19 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
CC:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	shemminger@...tta.com, netdev@...r.kernel.org
Subject: [PATCH] ipv4: arp_notify address list bug

From: Stephen Hemminger <shemminger@...tta.com>

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@...essinduktion.org>
Signed-off-by: Stephen Hemminger <shemminger@...tta.com>
Signed-off-by: Eric Dumazet <eric.dumazet@...il.com>
---
 net/ipv4/devinet.c |   16 ++++++++++------
 1 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index e92f1fd..5df2f6a 100644
--- 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);
--
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