bridge: Prevent insertion of FDB entry with disallowed vlan

br_handle_local_finish() is allowing us to insert an FDB entry with
disallowed vlan. For example, when port 1 and 2 are communicating in
vlan 10, and even if vlan 10 is disallowed on port 3, port 3 can
interfere with their communication by spoofed src mac address with
vlan id 10.

Note: Even if it is judged that a frame should not be learned, it should
not be dropped because it is destined for not forwarding layer but higher
layer. See IEEE 802.1Q-2011 8.13.10.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Acked-by: Vlad Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 28 insertions, 0 deletions

diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 4a37161..5fee2fe 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -241,6 +241,34 @@ bool br_allowed_egress(struct net_bridge *br,
 	return false;
 }
 
+/* Called under RCU */
+bool br_should_learn(struct net_bridge_port *p, struct sk_buff *skb, u16 *vid)
+{
+	struct net_bridge *br = p->br;
+	struct net_port_vlans *v;
+
+	if (!br->vlan_enabled)
+		return true;
+
+	v = rcu_dereference(p->vlan_info);
+	if (!v)
+		return false;
+
+	br_vlan_get_tag(skb, vid);
+	if (!*vid) {
+		*vid = br_get_pvid(v);
+		if (*vid == VLAN_N_VID)
+			return false;
+
+		return true;
+	}
+
+	if (test_bit(*vid, v->vlan_bitmap))
+		return true;
+
+	return false;
+}
+
 /* Must be protected by RTNL.
  * Must be called with vid in range from 1 to 4094 inclusive.
  */