From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0ACE9C433EF for ; Wed, 20 Oct 2021 15:54:24 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA0CE611B0 for ; Wed, 20 Oct 2021 15:54:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230219AbhJTP4h (ORCPT ); Wed, 20 Oct 2021 11:56:37 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43084 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229952AbhJTP4g (ORCPT ); Wed, 20 Oct 2021 11:56:36 -0400 Received: from fieldses.org (fieldses.org [IPv6:2600:3c00:e000:2f7::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 67989C06161C for ; Wed, 20 Oct 2021 08:54:22 -0700 (PDT) Received: by fieldses.org (Postfix, from userid 2815) id 1ED356CD2; Wed, 20 Oct 2021 11:54:21 -0400 (EDT) DKIM-Filter: OpenDKIM Filter v2.11.0 fieldses.org 1ED356CD2 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=fieldses.org; s=default; t=1634745261; bh=xbbaLfjoA8xE5hiaOT8uMLUrYO+8KshP2SMZpcZczk8=; h=Date:To:Cc:Subject:From:From; b=EtFF/B+34JAnqz/9TFOJ48Dlgc4USlnhU0DDRzU2DzZVcPoG//jq7F9oJoj9T+JC3 ezca6ZiRUFzK2ZPWDaAdCmhZ7JouMH+vdep7m66493PYifDNrPcrpN6iLdL10afF9w TgYFrSF43yMFZbYXeH/ILGsbGBtiS5uY1pfmXhvA= Date: Wed, 20 Oct 2021 11:54:21 -0400 To: linux-nfs@vger.kernel.org Cc: dai.ngo@oracle.com, Olga Kornievskaia , Steve Dickson , Chuck Lever Subject: server-to-server copy by default Message-ID: <20211020155421.GC597@fieldses.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) From: bfields@fieldses.org (J. Bruce Fields) Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org knfsd has supported server-to-server copy for a couple years (since 5.5). You have set a module parameter to enable it. I'm getting asked when we could turn that parameter on by default. I've got a couple vague criteria: one just general maturity, the other a security question: 1. General maturity: the only reports I recall seeing are from testers. Is anyone using this? Does it work for them? Do they find a benefit? Maybe we could turn it on by default in one distro (Fedora?) and promote it a little and see what that turns up? 2. Security question: with server-to-server copy enabled, you can send the server a COPY call with any random address, and the server will mount that address, open a file, and read from it. Is that safe? Normally we only mount servers that were chosen by root. Here we'll mount any random server that some client told us to. What's the worst that random server can do? Do we trust our xdr decoding? Can it DOS us by throwing the client's state recovery code into some loop with weird error returns? Etc. Maybe it's fine. I'm OK with some level of risk. I just want to make sure somebody's thought this through. There's also interest in allowing unprivileged NFS mounts, but I don't think we've turned that on yet, partly for similar reasons. This is a subset of that problem. --b.