ip6_tunnel: fix possible use-after-free on xmit
authorHaishuang Yan <yanhaishuang@cmss.chinamobile.com>
Thu, 25 Jul 2019 16:40:17 +0000 (00:40 +0800)
committerDavid S. Miller <davem@davemloft.net>
Fri, 26 Jul 2019 21:17:44 +0000 (14:17 -0700)
ip4ip6/ip6ip6 tunnels run iptunnel_handle_offloads on xmit which
can cause a possible use-after-free accessing iph/ipv6h pointer
since the packet will be 'uncloned' running pskb_expand_head if
it is a cloned gso skb.

Fixes: 0e9a709560db ("ip6_tunnel, ip6_gre: fix setting of DSCP on encapsulated packets")
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
net/ipv6/ip6_tunnel.c

index 3134fbb..754a484 100644 (file)
@@ -1278,12 +1278,11 @@ ip4ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
        }
 
        fl6.flowi6_uid = sock_net_uid(dev_net(dev), NULL);
+       dsfield = INET_ECN_encapsulate(dsfield, ipv4_get_dsfield(iph));
 
        if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6))
                return -1;
 
-       dsfield = INET_ECN_encapsulate(dsfield, ipv4_get_dsfield(iph));
-
        skb_set_inner_ipproto(skb, IPPROTO_IPIP);
 
        err = ip6_tnl_xmit(skb, dev, dsfield, &fl6, encap_limit, &mtu,
@@ -1367,12 +1366,11 @@ ip6ip6_tnl_xmit(struct sk_buff *skb, struct net_device *dev)
        }
 
        fl6.flowi6_uid = sock_net_uid(dev_net(dev), NULL);
+       dsfield = INET_ECN_encapsulate(dsfield, ipv6_get_dsfield(ipv6h));
 
        if (iptunnel_handle_offloads(skb, SKB_GSO_IPXIP6))
                return -1;
 
-       dsfield = INET_ECN_encapsulate(dsfield, ipv6_get_dsfield(ipv6h));
-
        skb_set_inner_ipproto(skb, IPPROTO_IPV6);
 
        err = ip6_tnl_xmit(skb, dev, dsfield, &fl6, encap_limit, &mtu,