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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id A8640C3F2C6 for ; Tue, 3 Mar 2020 11:57:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8430F206E6 for ; Tue, 3 Mar 2020 11:57:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729122AbgCCL5D (ORCPT ); Tue, 3 Mar 2020 06:57:03 -0500 Received: from youngberry.canonical.com ([91.189.89.112]:39494 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725818AbgCCL5D (ORCPT ); Tue, 3 Mar 2020 06:57:03 -0500 Received: from ip5f5bf7ec.dynamic.kabel-deutschland.de ([95.91.247.236] helo=wittgenstein) by youngberry.canonical.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.86_2) (envelope-from ) id 1j96AO-0000th-AQ; Tue, 03 Mar 2020 11:56:52 +0000 Date: Tue, 3 Mar 2020 12:56:51 +0100 From: Christian Brauner To: Miklos Szeredi Cc: David Howells , Ian Kent , James Bottomley , Steven Whitehouse , Miklos Szeredi , viro , Christian Brauner , Jann Horn , "Darrick J. Wong" , Linux API , linux-fsdevel , lkml , Greg Kroah-Hartman Subject: Re: [PATCH 00/17] VFS: Filesystem information and notifications [ver #17] Message-ID: <20200303115651.j5q7bsvzu5mstgw4@wittgenstein> References: <107666.1582907766@warthog.procyon.org.uk> <0403cda7345e34c800eec8e2870a1917a8c07e5c.camel@themaw.net> <1509948.1583226773@warthog.procyon.org.uk> <20200303100045.zqntjjjv6npvs5zl@wittgenstein> <20200303102541.diud7za3vvjvqco4@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 03, 2020 at 12:33:48PM +0100, Miklos Szeredi wrote: > On Tue, Mar 3, 2020 at 11:25 AM Christian Brauner > wrote: > > > > On Tue, Mar 03, 2020 at 11:13:50AM +0100, Miklos Szeredi wrote: > > > On Tue, Mar 3, 2020 at 11:00 AM Christian Brauner > > > wrote: > > > > > More magic links to beam you around sounds like a bad idea. We had a > > > > bunch of CVEs around them in containers and they were one of the major > > > > reasons behind us pushing for openat2(). That's why it has a > > > > RESOLVE_NO_MAGICLINKS flag. > > > > > > No, that link wouldn't beam you around at all, it would end up in an > > > internally mounted instance of a mountfs, a safe place where no > > > > Even if it is a magic link to a safe place it's a magic link. They > > aren't a great solution to this problem. fsinfo() is cleaner and > > simpler as it creates a context for a supervised mount which gives the a > > managing application fine-grained control and makes it easily > > extendable. > > Yeah, it's a nice and clean interface in the ioctl(2) sense. Sure, > fsinfo() is way better than ioctl(), but it at the core it's still the > same syscall multiplexer, do everything hack. In contrast to a generic ioctl() it's a domain-specific separate syscall. You can't suddenly set kvm options through fsinfo() I would hope. I find it at least debatable that a new filesystem is preferable. And - feel free to simply dismiss the concerns I expressed - so far there has not been a lot of excitement about this idea. > > > Also, we're apparently at the point where it seems were suggesting > > another (pseudo)filesystem to get information about filesystems. > > Implementation detail. Why would you care? I wouldn't call this an implementation detail. That's quite a big design choice; it's a separate fileystem. In addition, implementation details need to be maintained. Christian