--- x/net/batman-adv/netlink.c
+++ y/net/batman-adv/netlink.c
@@ -495,7 +495,9 @@ static int batadv_netlink_set_mesh(struc
 		attr = info->attrs[BATADV_ATTR_FRAGMENTATION_ENABLED];
 
 		atomic_set(&bat_priv->fragmentation, !!nla_get_u8(attr));
+		rtnl_lock();
 		batadv_update_min_mtu(bat_priv->soft_iface);
+		rtnl_unlock();
 	}
 
 	if (info->attrs[BATADV_ATTR_GW_BANDWIDTH_DOWN]) {