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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AA6F9C7EE23 for ; Tue, 23 May 2023 23:46:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233337AbjEWXqQ (ORCPT ); Tue, 23 May 2023 19:46:16 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55760 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229539AbjEWXqP (ORCPT ); Tue, 23 May 2023 19:46:15 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B40F190; Tue, 23 May 2023 16:46:14 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4623C63581; Tue, 23 May 2023 23:46:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 65EE2C433EF; Tue, 23 May 2023 23:46:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1684885573; bh=hy6VE9loTK6zmHLdZEYYJlKXBdhGlHAMSBuVMqSkYR8=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eUzzM5yl0hW5QdsTB+hdJwUiYiWlArc/Z7PL4V8BGkzM+OW28urXzmJ3/BZZ2m2qb 2QTaWtjlh+Jnvy43jTuAqN93tR3z7cQcN9/VPc2w4rGJUIkdARMhDa93/rBdOLcvTJ 2Cqq5IIcYfzsDZ2FGqzQ8/rR8ZEWVNS2GXqpbtfSDHDKYcZvtzXov6BIdv40zZB27n qILKIetEW4Fb2D4pd5ZENfN2yhPLSJpDlboP8G/m4cZG9vj+o71nPgIQl59S+/xpJL iRpO9tdfB+Brib5lxkD4qkG0m6aHf6gjPysmJoyVYTfuEWKIWLDvGOymuNwW+mE9+c MCYuJY9eCaZBQ== Date: Tue, 23 May 2023 23:46:12 +0000 From: Eric Biggers To: Dave Chinner Cc: "Darrick J. Wong" , Bagas Sanjaya , Pengfei Xu , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, heng.su@intel.com, dchinner@redhat.com, lkp@intel.com, Linux Regressions Subject: Re: [Syzkaller & bisect] There is BUG: unable to handle kernel NULL pointer dereference in xfs_extent_free_diff_items in v6.4-rc3 Message-ID: <20230523234612.GG888341@google.com> References: <20230522160525.GB11620@frogsfrogsfrogs> <20230523000029.GB3187780@google.com> <20230523165044.GA862686@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On Wed, May 24, 2023 at 08:16:58AM +1000, Dave Chinner wrote: > config XFS_SUPPORT_V4 > bool "Support deprecated V4 (crc=0) format" > depends on XFS_FS > default y > help > The V4 filesystem format lacks certain features that are supported > by the V5 format, such as metadata checksumming, strengthened > metadata verification, and the ability to store timestamps past the > year 2038. Because of this, the V4 format is deprecated. All users > should upgrade by backing up their files, reformatting, and restoring > from the backup. > > Administrators and users can detect a V4 filesystem by running > xfs_info against a filesystem mountpoint and checking for a string > beginning with "crc=". If the string "crc=0" is found, the > filesystem is a V4 filesystem. If no such string is found, please > upgrade xfsprogs to the latest version and try again. > > This option will become default N in September 2025. Support for the > V4 format will be removed entirely in September 2030. Distributors > can say N here to withdraw support earlier. > > To continue supporting the old V4 format (crc=0), say Y. > To close off an attack surface, say N. > > This was added almost 3 years ago in mid-2020. We're more than half > way through the deprecation period and then we're going to turn off > v4 support by default. At this point, nobody should be using v4 > filesystems in new production systems, and those that are should be > preparing for upstream and distro support to be withdraw in the next > couple of years... Great to see that this exists now and there is a specific deprecation plan! > > Then you could just tell the people fuzzing XFS filesystem images > > that they need to use that option. That would save everyone a lot of time. > > (To be clear, I'm not arguing for the XFS policy on v4 filesystems being right > > or wrong; that's really not something I'd like to get into again... I'm just > > saying that if that's indeed your policy, this is what you should do.) > > It should be obvious by now that we've already done this. 3 years > ago, in fact. And yet we are still having the same problems. Maybe > this helps you understand the level of frustration we have with all > the people running fuzzing bots out there.... I don't see evidence that this actually happened, though perhaps we are not looking in the same places. https://lore.kernel.org/all/?q=XFS_SUPPORT_V4 brings up little except the original patch thread, nor did https://github.com/search?q=XFS_SUPPORT_V4&type=issues find anything. Anyway, I took 3 minutes to file an issue in the syzkaller repo (https://github.com/google/syzkaller/issues/3918), so at least this should get resolved for syzbot soon. - Eric