batman-adv: Disallow regular interface as mesh device

When trying to associate a net_device with another net_device which
already exists, batman-adv assumes that this interface is a fully
initialized batman mesh interface without checking it. The behaviour
when accessing data behind netdev_priv of a random net_device is
undefined and potentially dangerous.

Reported-by: Linus Lüssing <linus.luessing@ascom.ch>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>

1 files changed, 13 insertions, 0 deletions

diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 6b514ecee5a2..9ed26140a269 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -622,6 +622,19 @@ void softif_destroy(struct net_device *soft_iface)
         unregister_netdevice(soft_iface);
 }
 
+int softif_is_valid(struct net_device *net_dev)
+{
+#ifdef HAVE_NET_DEVICE_OPS
+        if (net_dev->netdev_ops->ndo_start_xmit == interface_tx)
+                return 1;
+#else
+        if (net_dev->hard_start_xmit == interface_tx)
+                return 1;
+#endif
+
+        return 0;
+}
+
 /* ethtool */
 static int bat_get_settings(struct net_device *dev, struct ethtool_cmd *cmd)
 {