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[49.195.66.88]) by smtp.gmail.com with ESMTPSA id u10-20020a170902e80a00b001aadd0d7364sm11707517plg.83.2023.09.06.19.22.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 06 Sep 2023 19:22:45 -0700 (PDT) Received: from dave by dread.disaster.area with local (Exim 4.96) (envelope-from ) id 1qe4fL-00BqCW-1c; Thu, 07 Sep 2023 12:22:43 +1000 Date: Thu, 7 Sep 2023 12:22:43 +1000 From: Dave Chinner To: Steven Rostedt Cc: Guenter Roeck , Christoph Hellwig , ksummit@lists.linux.dev, linux-fsdevel@vger.kernel.org Subject: Re: [MAINTAINERS/KERNEL SUMMIT] Trust and maintenance of file systems Message-ID: References: <8718a8a3-1e62-0e2b-09d0-7bce3155b045@roeck-us.net> <20230906215327.18a45c89@gandalf.local.home> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230906215327.18a45c89@gandalf.local.home> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org On Wed, Sep 06, 2023 at 09:53:27PM -0400, Steven Rostedt wrote: > On Thu, 7 Sep 2023 08:54:38 +1000 > Dave Chinner wrote: > > > And let's not forget: removing a filesystem from the kernel is not > > removing end user support for extracting data from old filesystems. > > We have VMs for that - we can run pretty much any kernel ever built > > inside a VM, so users that need to extract data from a really old > > filesystem we no longer support in a modern kernel can simply boot > > up an old distro that did support it and extract the data that way. > > Of course there's the case of trying to recreate a OS that can run on a > very old kernel. Just building an old kernel is difficult today because > today's compilers will refuse to build them (I've hit issues in bisections > because of that!) > > You could argue that you could just install an old OS into the VM, but that > too requires access to that old OS. Well, yes - why would anyone even bother trying to build an ancient kernel when all they need to do is download an iso and point the VM at it? > Anyway, what about just having read-only be the minimum for supporting a > file system? We can say "sorry, due to no one maintaining this file system, > we will no longer allow write access." But I'm guessing that just > supporting reading an old file system is much easier than modifying one > (wasn't that what we did with NTFS for the longest time?) "Read only" doesn't mean the filesytsem implementation is in any way secure, robust or trustworthy - the kernel is still parsing untrusted data in ring 0 using unmaintained, bit-rotted, untested code.... -Dave. -- Dave Chinner david@fromorbit.com