bridge: prevent bridging wrong device

The bridge code assumes ethernet addressing, so be more strict in
the what is allowed. This showed up when GRE had a bug and was not
using correct address format.

Add some more comments for increased clarity.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 1 deletions

diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index b1b3b0fbf41c..4a9f52732655 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -377,12 +377,16 @@ int br_add_if(struct net_bridge *br, struct net_device *dev)
         struct net_bridge_port *p;
         int err = 0;
 
-        if (dev->flags & IFF_LOOPBACK || dev->type != ARPHRD_ETHER)
+        /* Don't allow bridging non-ethernet like devices */
+        if ((dev->flags & IFF_LOOPBACK) ||
+            dev->type != ARPHRD_ETHER || dev->addr_len != ETH_ALEN)
                 return -EINVAL;
 
+        /* No bridging of bridges */
         if (dev->netdev_ops->ndo_start_xmit == br_dev_xmit)
                 return -ELOOP;
 
+        /* Device is already being bridged */
         if (dev->br_port != NULL)
                 return -EBUSY;