ipv4/route: fail early when inet dev is missing

If a non local multicast packet reaches ip_route_input_rcu() while the ingress device IPv4 private data (in_dev) is NULL, we end up doing a NULL pointer dereference in IN_DEV_MFORWARD(). Since the later call to ip_route_input_mc() is going to fail if !in_dev, we can fail early in such scenario and avoid the dangerous code path. v1 -> v2: - clarified the commit message, no code changes Reported-by: Tianhao Zhao <[email protected]> Fixes: e58e415 ("net: Enable support for VRF with ipv4 multicast") Signed-off-by: Paolo Abeni <[email protected]> Reviewed-by: David Ahern <[email protected]> Signed-off-by: David S. Miller <[email protected]>
kinvolk · Mar 6, 2019 · 22c7476 · 22c7476
1 parent f4772de
commit 22c7476
Showing 1 changed file with 5 additions and 4 deletions.
diff --git a/net/ipv4/route.c b/net/ipv4/route.c
@@ -2149,12 +2149,13 @@ int ip_route_input_rcu(struct sk_buff *skb, __be32 daddr, __be32 saddr,
 		int our = 0;
 		int err = -EINVAL;
 
-		if (in_dev)
-			our = ip_check_mc_rcu(in_dev, daddr, saddr,
-					      ip_hdr(skb)->protocol);
+		if (!in_dev)
+			return err;
+		our = ip_check_mc_rcu(in_dev, daddr, saddr,
+				      ip_hdr(skb)->protocol);
 
 		/* check l3 master if no match yet */
-		if ((!in_dev || !our) && netif_is_l3_slave(dev)) {
+		if (!our && netif_is_l3_slave(dev)) {
 			struct in_device *l3_in_dev;
 
 			l3_in_dev = __in_dev_get_rcu(skb->dev);