[NETFILTER]: H.323 helper: fix possible NULL-ptr dereference

An RCF message containing a timeout results in a NULL-ptr dereference if
no RRQ has been seen before.

Noticed by the "SATURN tool", reported by Thomas Dillig <tdillig@stanford.edu>
and Isil Dillig <isil@stanford.edu>.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/netfilter/ip_conntrack_helper_h323.c b/net/ipv4/netfilter/ip_conntrack_helper_h323.c
index af35235..9a39e29 100644 (file)
--- a/net/ipv4/netfilter/ip_conntrack_helper_h323.c
+++ b/net/ipv4/netfilter/ip_conntrack_helper_h323.c
@@ -1200,7 +1200,7 @@ static struct ip_conntrack_expect *find_expect(struct ip_conntrack *ct,
        tuple.dst.protonum = IPPROTO_TCP;
 
        exp = __ip_conntrack_expect_find(&tuple);
-       if (exp->master == ct)
+       if (exp && exp->master == ct)
                return exp;
        return NULL;
 }