--- x/net/batman-adv/hard-interface.c
+++ y/net/batman-adv/hard-interface.c
@@ -642,7 +642,9 @@ void batadv_update_min_mtu(struct net_de
 		limit_mtu = ETH_DATA_LEN;
 
 	mtu = min(mtu, limit_mtu);
+	rtnl_lock();
 	dev_set_mtu(soft_iface, mtu);
+	rtnl_unlock();
 
 	/* Check if the local translate table should be cleaned up to match a
 	 * new (and smaller) MTU.