ip_tunnel: Fix dst ref-count.

Commit 10ddceb22ba (ip_tunnel:multicast process cause panic due
to skb->_skb_refdst NULL pointer) removed dst-drop call from
ip-tunnel-recv.

Following commit reintroduce dst-drop and fix the original bug by
checking loopback packet before releasing dst.
Original bug: https://bugzilla.kernel.org/show_bug.cgi?id=70681

CC: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 9 insertions, 3 deletions

diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index 1863422fb7d5..250be7421ab3 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -182,6 +182,14 @@ static int gre_cisco_rcv(struct sk_buff *skb)
         int i;
         bool csum_err = false;
 
+#ifdef CONFIG_NET_IPGRE_BROADCAST
+        if (ipv4_is_multicast(ip_hdr(skb)->daddr)) {
+                /* Looped back packet, drop it! */
+                if (rt_is_output_route(skb_rtable(skb)))
+                        goto drop;
+        }
+#endif
+
         if (parse_gre_header(skb, &tpi, &csum_err) < 0)
                 goto drop;
 
diff --git a/net/ipv4/ip_tunnel.c b/net/ipv4/ip_tunnel.c
index 78a89e61925d..a82a22d8f77f 100644
--- a/net/ipv4/ip_tunnel.c
+++ b/net/ipv4/ip_tunnel.c
@@ -416,9 +416,6 @@ int ip_tunnel_rcv(struct ip_tunnel *tunnel, struct sk_buff *skb,
 
 #ifdef CONFIG_NET_IPGRE_BROADCAST
         if (ipv4_is_multicast(iph->daddr)) {
-                /* Looped back packet, drop it! */
-                if (rt_is_output_route(skb_rtable(skb)))
-                        goto drop;
                 tunnel->dev->stats.multicast++;
                 skb->pkt_type = PACKET_BROADCAST;
         }
diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c
index 6f847dd56dbc..8d69626f2206 100644
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -108,6 +108,7 @@ int iptunnel_pull_header(struct sk_buff *skb, int hdr_len, __be16 inner_proto)
         nf_reset(skb);
         secpath_reset(skb);
         skb_clear_hash_if_not_l4(skb);
+        skb_dst_drop(skb);
         skb->vlan_tci = 0;
         skb_set_queue_mapping(skb, 0);
         skb->pkt_type = PACKET_HOST;