Staging: batman-adv: only modify hna-table on active module

If we haven't set the module to MODULE_ACTIVE state before (in general,
no interface has yet been added to batman-adv) then the hna table is not
initialised yet. If the kernel changes the mac address of the bat0
interface at this moment then an hna_local_add() called by interface_set_mac_addr()
then resulted in a null pointer derefernce. With this patch we are now
explicitly checking before if the state is MODULE_ACTIVE right now so
that we can assume having an initialised hna table.
Signed-off-by: Linus Lüssing <linus.luessing@web.de>
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/batman-adv/soft-interface.c

@@ -152,9 +152,13 @@ int interface_set_mac_addr(struct net_device *dev, void *p)
 	if (!is_valid_ether_addr(addr->sa_data))
 		return -EADDRNOTAVAIL;
 
-	hna_local_remove(dev->dev_addr, "mac address changed");
+	/* only modify hna-table if it has been initialised before */
+	if (atomic_read(&module_state) == MODULE_ACTIVE) {
+		hna_local_remove(dev->dev_addr, "mac address changed");
+		hna_local_add(addr->sa_data);
+	}
+
 	memcpy(dev->dev_addr, addr->sa_data, ETH_ALEN);
-	hna_local_add(dev->dev_addr);
 
 	return 0;
 }