Subject: [PATCH] nethost ipv4: Don't allow global ipv4 addresses that another nethost is already using.
From: Eric W. Biederman <ebiederman@lnxi.com>
Date: 1134399578 -0700

---

 net/ipv4/devinet.c |   38 +++++++++++++++++++++++++++++++++++++-
 1 files changed, 37 insertions(+), 1 deletions(-)

2c69965eabaee127f4bfafa745b0bb7cb12c21e6
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 139b23c..e3345bc 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -183,8 +183,9 @@ static void in_dev_rcu_put(struct rcu_he
 
 static void inethost_destroy(struct nethost *host)
 {
-	/* FIXME is the locking correct in this function? */
 	struct net_device *dev;
+	ASSERT_RTNL();
+
 	if (!host)
 		return;
 	read_lock(&dev_base_lock);
@@ -330,6 +331,34 @@ static void inet_del_ifa(struct in_devic
 	}
 }
 
+static int inet_chk_same_host_addr(u32 addr, struct in_device *adev,
+				   struct nethost *host)
+{
+	struct net_device *dev;
+	struct in_ifaddr *ifa = NULL;
+
+	read_lock(&dev_base_lock);
+	rcu_read_lock();
+	for (dev = dev_base; dev; dev = dev->next) {
+		struct in_device *idev;
+		if ((idev = __in_dev_get_rcu(dev)) == NULL)
+			continue;
+		for(ifa = idev->ifa_list; ifa; ifa = ifa->ifa_next) {
+			if (ifa->ifa_local == addr) {
+				if (adev == NULL || ifa->ifa_dev == adev)
+					goto out;
+				if (host && (ifa->ifa_host != host) && 
+				    (ifa->ifa_scope < RT_SCOPE_LINK))
+					goto out;
+			}
+		}
+	}
+ out:
+	rcu_read_unlock();
+	read_unlock(&dev_base_lock);
+	return ifa != NULL;
+}
+
 static int inet_insert_ifa(struct in_ifaddr *ifa)
 {
 	struct in_device *in_dev = ifa->ifa_dev;
@@ -342,6 +371,13 @@ static int inet_insert_ifa(struct in_ifa
 		return 0;
 	}
 
+	/* Deny adding duplicate address on a interface */
+	/* Deny adding global addresses already used by another host */
+	if (inet_chk_same_host_addr(ifa->ifa_local, ifa->ifa_dev, ifa->ifa_host)) {
+		inet_free_ifa(ifa);
+		return -EEXIST;
+	}
+
 	/* 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)) {
-- 
1.0.GIT