netfilter: nf_conntrack: fix ct refcount leak in l4proto->error()

This patch fixes a refcount leak of ct objects that may occur if
l4proto->error() assigns one conntrack object to one skbuff. In
that case, we have to skip further processing in nf_conntrack_in().

With this patch, we can also fix wrong return values (-NF_ACCEPT)
for special cases in ICMP[v6] that should not bump the invalid/error
statistic counters.

Reported-by: Zoltan Menyhart <Zoltan.Menyhart@bull.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

3 files changed, 5 insertions, 2 deletions

diff --git a/net/ipv4/netfilter/nf_conntrack_proto_icmp.c b/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
index 7404bde95994..ab5b27a2916f 100644
--- a/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
+++ b/net/ipv4/netfilter/nf_conntrack_proto_icmp.c
@@ -160,7 +160,7 @@ icmp_error_message(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
         /* Update skb to refer to this connection */
         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
         skb->nfctinfo = *ctinfo;
-        return -NF_ACCEPT;
+        return NF_ACCEPT;
 }
 
 /* Small and modified version of icmp_rcv */
diff --git a/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c b/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
index 1df3c8b6bf47..7c05e7eacbc6 100644
--- a/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
+++ b/net/ipv6/netfilter/nf_conntrack_proto_icmpv6.c
@@ -177,7 +177,7 @@ icmpv6_error_message(struct net *net, struct nf_conn *tmpl,
         /* Update skb to refer to this connection */
         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
         skb->nfctinfo = *ctinfo;
-        return -NF_ACCEPT;
+        return NF_ACCEPT;
 }
 
 static int
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 0bd568929403..f7af8b866017 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -922,6 +922,9 @@ nf_conntrack_in(struct net *net, u_int8_t pf, unsigned int hooknum,
                         ret = -ret;
                         goto out;
                 }
+                /* ICMP[v6] protocol trackers may assign one conntrack. */
+                if (skb->nfct)
+                        goto out;
         }
 
         ct = resolve_normal_ct(net, tmpl, skb, dataoff, pf, protonum,