Subject: [PATCH] nethost: ipv4 more correct loopback device handling.
From: Eric W. Biederman <ebiederman@lnxi.com>
Date: 1134241610 -0700

Always detect the loopback devince with IFF_LOOBACK.
Don't allow putting addresses for other hosts on the loopback device.

---

 net/ipv4/devinet.c |   13 ++++++++++---
 1 files changed, 10 insertions(+), 3 deletions(-)

6553b6aca63ece06d193dfb0d5fdeb1b231bf261
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 0b8e7ca..28db04d 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -183,7 +183,7 @@ static void in_dev_rcu_put(struct rcu_he
 
 static void inethost_destroy(struct nethost *host)
 {
-	/* FIXME is the lock correct in this function? */
+	/* FIXME is the locking correct in this function? */
 	struct net_device *dev;
 	if (!host)
 		return;
@@ -342,6 +342,13 @@ static int inet_insert_ifa(struct in_ifa
 		return 0;
 	}
 
+	/* Deny adding addresses owned by other hosts to the loopback device */
+	if ((ifa->ifa_dev->dev->flags & IFF_LOOPBACK) && 
+	    (ifa->ifa_dev->dev != &ifa->ifa_host->loopback_dev)) {
+		inet_free_ifa(ifa);
+		return -EINVAL;
+	}
+
 	ifa->ifa_flags &= ~IFA_F_SECONDARY;
 	last_primary = &in_dev->ifa_list;
 
@@ -1050,7 +1057,7 @@ static int inetdev_event(struct notifier
 	ASSERT_RTNL();
 
 	if (!in_dev) {
-		if (event == NETDEV_REGISTER && dev->type == ARPHRD_LOOPBACK) {
+		if (event == NETDEV_REGISTER && (dev->flags & IFF_LOOPBACK)) {
 			in_dev = inetdev_init(dev);
 			if (!in_dev)
 				panic("devinet: Failed to create loopback\n");
@@ -1068,7 +1075,7 @@ static int inetdev_event(struct notifier
 	case NETDEV_UP:
 		if (dev->mtu < 68)
 			break;
-		if (dev->type == ARPHRD_LOOPBACK) {
+		if (dev->flags & IFF_LOOPBACK) {
 			struct in_ifaddr *ifa;
 			if ((ifa = inet_alloc_ifa()) != NULL) {
 				ifa->ifa_host = loopback_host(dev);
-- 
1.0.GIT