Toshiaki Makita
2014-May-26 06:15 UTC
[PATCH net] 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>
---
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 7985dea..04d6348 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -147,8 +147,8 @@ 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, false);
return 0; /* process further */
}
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 06811d7..59d3a85 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -581,6 +581,7 @@ bool br_allowed_ingress(struct net_bridge *br, struct
net_port_vlans *v,
struct sk_buff *skb, u16 *vid);
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);
struct sk_buff *br_handle_vlan(struct net_bridge *br,
const struct net_port_vlans *v,
struct sk_buff *skb);
@@ -648,6 +649,12 @@ 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 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.
*/
--
1.8.1.2