netfilter: make it safer during the inet6_dev->addr_list traversal

inet6_dev->addr_list is protected by inet6_dev->lock, so only using
rcu_read_lock is not enough, we should acquire read_lock_bh(&idev->lock)
before the inet6_dev->addr_list traversal.
Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_nat_redirect.c

@@ -101,11 +101,13 @@ nf_nat_redirect_ipv6(struct sk_buff *skb, const struct nf_nat_range *range,
 		rcu_read_lock();
 		idev = __in6_dev_get(skb->dev);
 		if (idev != NULL) {
+			read_lock_bh(&idev->lock);
 			list_for_each_entry(ifa, &idev->addr_list, if_list) {
 				newdst = ifa->addr;
 				addr = true;
 				break;
 			}
+			read_unlock_bh(&idev->lock);
 		}
 		rcu_read_unlock();
 

net/netfilter/xt_TPROXY.c

@@ -393,7 +393,8 @@ tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr,
 
 	rcu_read_lock();
 	indev = __in6_dev_get(skb->dev);
-	if (indev)
+	if (indev) {
+		read_lock_bh(&indev->lock);
 		list_for_each_entry(ifa, &indev->addr_list, if_list) {
 			if (ifa->flags & (IFA_F_TENTATIVE | IFA_F_DEPRECATED))
 				continue;
@@ -401,6 +402,8 @@ tproxy_laddr6(struct sk_buff *skb, const struct in6_addr *user_laddr,
 			laddr = &ifa->addr;
 			break;
 		}
+		read_unlock_bh(&indev->lock);
+	}
 	rcu_read_unlock();
 
 	return laddr ? laddr : daddr;