[PATCH 3.16 006/294] net: bridge: fix dest lookup when vlan proto doesn't match

[Ben Hutchings]

3.16.50-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>

commit 31a4562d7408493c6377933ff2f7d7302dbdea80 upstream.

With 802.1ad support the vlan_ingress code started checking for vlan
protocol mismatch which causes the current tag to be inserted and the
bridge vlan protocol & pvid to be set. The vlan tag insertion changes
the skb mac_header and thus the lookup mac dest pointer which was loaded
prior to calling br_allowed_ingress in br_handle_frame_finish is VLAN_HLEN
bytes off now, pointing to the last two bytes of the destination mac and
the first four of the source mac causing lookups to always fail and
broadcasting all such packets to all ports. Same thing happens for locally
originated packets when passing via br_dev_xmit. So load the dest pointer
after the vlan checks and possible skb change.

Fixes: 8580e2117c06 ("bridge: Prepare for 802.1ad vlan filtering support")
Reported-by: Anitha Narasimha Murthy <anitha@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Nikolay Aleksandrov <nikolay@xxxxxxxxxxxxxxxxxxx>
Acked-by: Toshiaki Makita <makita.toshiaki@xxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/bridge/br_device.c | 3 ++-
 net/bridge/br_input.c  | 3 ++-
 2 files changed, 4 insertions(+), 2 deletions(-)

--- a/net/bridge/br_device.c
+++ b/net/bridge/br_device.c
@@ -31,10 +31,10 @@ static struct lock_class_key bridge_netd
 netdev_tx_t br_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct net_bridge *br = netdev_priv(dev);
-	const unsigned char *dest = skb->data;
 	struct net_bridge_fdb_entry *dst;
 	struct net_bridge_mdb_entry *mdst;
 	struct pcpu_sw_netstats *brstats = this_cpu_ptr(br->stats);
+	const unsigned char *dest;
 	u16 vid = 0;
 
 	rcu_read_lock();
@@ -59,6 +59,7 @@ netdev_tx_t br_dev_xmit(struct sk_buff *
 	if (!br_allowed_ingress(br, br_get_vlan_info(br), skb, &vid))
 		goto out;
 
+	dest = eth_hdr(skb)->h_dest;
 	if (is_broadcast_ether_addr(dest))
 		br_flood_deliver(br, skb, false);
 	else if (is_multicast_ether_addr(dest)) {
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -60,11 +60,11 @@ static int br_pass_frame_up(struct sk_bu
 /* note: already called with rcu_read_lock */
 int br_handle_frame_finish(struct sk_buff *skb)
 {
-	const unsigned char *dest = eth_hdr(skb)->h_dest;
 	struct net_bridge_port *p = br_port_get_rcu(skb->dev);
 	struct net_bridge *br;
 	struct net_bridge_fdb_entry *dst;
 	struct net_bridge_mdb_entry *mdst;
+	const unsigned char *dest;
 	struct sk_buff *skb2;
 	bool unicast = true;
 	u16 vid = 0;
@@ -80,6 +80,7 @@ int br_handle_frame_finish(struct sk_buf
 	if (p->flags & BR_LEARNING)
 		br_fdb_update(br, p, eth_hdr(skb)->h_source, vid, false);
 
+	dest = eth_hdr(skb)->h_dest;
 	if (!is_broadcast_ether_addr(dest) && is_multicast_ether_addr(dest) &&
 	    br_multicast_rcv(br, p, skb, vid))
 		goto drop;