[PATCH 3.12 095/111] bridge: Prevent insertion of FDB entry with disallowed vlan

[Jiri Slaby]

From: Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx>

3.12-stable review patch.  If anyone has any objections, please let me know.

===============

[ Upstream commit e0d7968ab6c8bce2437b36fa7f04117e333f196d ]

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@xxxxxxxxxxxxx>
Acked-by: Vlad Yasevich <vyasevic@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
 net/bridge/br_input.c   |  4 ++--
 net/bridge/br_private.h |  7 +++++++
 net/bridge/br_vlan.c    | 28 ++++++++++++++++++++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index c378750602cd..1f59299921f8 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -146,8 +146,8 @@ static int br_handle_local_finish(struct sk_buff *skb)
 	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 	u16 vid = 0;
 
-	br_vlan_get_tag(skb, &vid);
-	if (p->flags & BR_LEARNING)
+	/* check if vlan is allowed, to avoid spoofing */
+	if (p->flags & BR_LEARNING && br_should_learn(p, skb, &vid))
 		br_fdb_update(p->br, p, eth_hdr(skb)->h_source, vid);
 	return 0;	 /* process further */
 }
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 9a63c4206e4a..de50e79b9c34 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -605,6 +605,7 @@ extern bool br_allowed_ingress(struct net_bridge *br, struct net_port_vlans *v,
 extern bool br_allowed_egress(struct net_bridge *br,
 			      const struct net_port_vlans *v,
 			      const struct sk_buff *skb);
+bool br_should_learn(struct net_bridge_port *p, struct sk_buff *skb, u16 *vid);
 extern struct sk_buff *br_handle_vlan(struct net_bridge *br,
 				      const struct net_port_vlans *v,
 				      struct sk_buff *skb);
@@ -671,6 +672,12 @@ static inline bool br_allowed_egress(struct net_bridge *br,
 	return true;
 }
 
+static inline bool br_should_learn(struct net_bridge_port *p,
+				   struct sk_buff *skb, u16 *vid)
+{
+	return true;
+}
+
 static inline struct sk_buff *br_handle_vlan(struct net_bridge *br,
 					     const struct net_port_vlans *v,
 					     struct sk_buff *skb)
diff --git a/net/bridge/br_vlan.c b/net/bridge/br_vlan.c
index 45a26debe64e..12ce54c0e8ed 100644
--- a/net/bridge/br_vlan.c
+++ b/net/bridge/br_vlan.c
@@ -260,6 +260,34 @@ 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.
  */
-- 
2.0.0

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