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=-2.5 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 25246C0650E for ; Mon, 1 Jul 2019 17:21:04 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EFC5E2146F for ; Mon, 1 Jul 2019 17:21:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=plexistor-com.20150623.gappssmtp.com header.i=@plexistor-com.20150623.gappssmtp.com header.b="1wUdmopY" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729274AbfGARU7 (ORCPT ); Mon, 1 Jul 2019 13:20:59 -0400 Received: from mail-wm1-f67.google.com ([209.85.128.67]:34109 "EHLO mail-wm1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726840AbfGARU7 (ORCPT ); Mon, 1 Jul 2019 13:20:59 -0400 Received: by mail-wm1-f67.google.com with SMTP id w9so518855wmd.1 for ; Mon, 01 Jul 2019 10:20:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=plexistor-com.20150623.gappssmtp.com; s=20150623; h=subject:to:cc:references:from:message-id:date:user-agent :mime-version:in-reply-to:content-language:content-transfer-encoding; bh=RMtO9zTMwULPwpFiTkeooNGzR9zKo/UB7YgL+t4fgzA=; b=1wUdmopYsOTGEBPctCCQBJNp/Weny3U0OdMAgIX7XMpDLNjX7yi2BQKVOeIOZfgf1b I2dQPvs1YcMd4MKfGasxoR1vUF57n1uWvGfOwCBn+dFFXqdtzk7+nDTMfgxaIC1cMqAd CyXSD5wWJrsSE7f66iNNQpS8suPAgj9SNlBFoRgvaYPLl2O9hulyvjxbO8s6Guhj4y1S Nf6nnLqhsslQUJQ8lQjHCR002MedRLPvKNFje/NywIlwBVxr1dbYLS/Ag6d45MoLEFLA TB43Jl9ECXn6C3ClznsgSlBckfDR8AQM1se/327D0FreZlmY9S9DkHpcHai8gVFUiAbk jAnQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=RMtO9zTMwULPwpFiTkeooNGzR9zKo/UB7YgL+t4fgzA=; b=XyrWa0S522F7/UcajGEYzCG0Yrz/I3VEvOuu+Yr19sSasbqinN4HacEc58AYZSS+bN iEJcif0KhQwCKg5vJ0mBaiUccMYUA0Lg8DAjX71W2giPstw78upcmGLHG99fo7KDKf7O zts3qsNbTcQfhyhHdB7pi++rrCg9/RqrcFO+QjjiinPVraWjeEwiE2ck8SOUeAjS+Xyp gO75f2/vYmaAzcEDTIHM0ly+T2TqAalItnI78DPrsIuv6dq7emqW7HLRChV+jeZhgfMA CyFi24LEmsvZee6cNbpvg1lIGfTu9ZuUgn/Rl+7Fn9odlmwjFAV0KF6Iq/GgKXGr8o4T vC/A== X-Gm-Message-State: APjAAAXcs4r+Ex1wLqHcWi3gssU1IL/3hRq5V5y4ZundGQhMbLyFSAHh aCiPkOGv2qk4EFFuhaRgKreSfA== X-Google-Smtp-Source: APXvYqyJIZEjZ99B+K6R50DPm7lq0IHr/E/1lfJMHdrHDPCDWuYMn1JV6lQAB5xdWdZjMaq23hnwbA== X-Received: by 2002:a1c:f009:: with SMTP id a9mr234245wmb.32.1562001657000; Mon, 01 Jul 2019 10:20:57 -0700 (PDT) Received: from [10.68.217.182] ([217.70.211.18]) by smtp.googlemail.com with ESMTPSA id q193sm269299wme.8.2019.07.01.10.20.53 (version=TLS1_3 cipher=AEAD-AES128-GCM-SHA256 bits=128/128); Mon, 01 Jul 2019 10:20:56 -0700 (PDT) Subject: Re: [PATCH v6 0/4] vfs: make immutable files actually immutable To: "Darrick J. Wong" , matthew.garrett@nebula.com, yuchao0@huawei.com, tytso@mit.edu, ard.biesheuvel@linaro.org, josef@toxicpanda.com, hch@infradead.org, clm@fb.com, adilger.kernel@dilger.ca, viro@zeniv.linux.org.uk, jack@suse.com, dsterba@suse.com, jaegeuk@kernel.org, jk@ozlabs.org Cc: reiserfs-devel@vger.kernel.org, linux-efi@vger.kernel.org, devel@lists.orangefs.org, linux-kernel@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-xfs@vger.kernel.org, linux-mm@kvack.org, linux-nilfs@vger.kernel.org, linux-mtd@lists.infradead.org, ocfs2-devel@oss.oracle.com, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org References: <156174687561.1557469.7505651950825460767.stgit@magnolia> From: Boaz Harrosh Message-ID: <72f01c73-a1eb-efde-58fa-7667221255c7@plexistor.com> Date: Mon, 1 Jul 2019 20:20:51 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <156174687561.1557469.7505651950825460767.stgit@magnolia> Content-Type: text/plain; charset=utf-8 Content-Language: en-MW Content-Transfer-Encoding: 7bit Sender: linux-ext4-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-ext4@vger.kernel.org On 28/06/2019 21:34, Darrick J. Wong wrote: > Hi all, > > The chattr(1) manpage has this to say about the immutable bit that > system administrators can set on files: > > "A file with the 'i' attribute cannot be modified: it cannot be deleted > or renamed, no link can be created to this file, most of the file's > metadata can not be modified, and the file can not be opened in write > mode." > > Given the clause about how the file 'cannot be modified', it is > surprising that programs holding writable file descriptors can continue > to write to and truncate files after the immutable flag has been set, > but they cannot call other things such as utimes, fallocate, unlink, > link, setxattr, or reflink. > > Since the immutable flag is only settable by administrators, resolve > this inconsistent behavior in favor of the documented behavior -- once > the flag is set, the file cannot be modified, period. We presume that > administrators must be trusted to know what they're doing, and that > cutting off programs with writable fds will probably break them. > This effort sounds very logical to me and sound. But are we allowed to do it? IE: Is it not breaking ABI. I do agree previous ABI was evil but are we allowed to break it? I would not mind breaking it if %99.99 of the time the immutable bit was actually set manually by a human administrator. But what if there are automated systems that set it relying on the current behaviour? For example I have a very distant and vague recollection of a massive camera capture system, that was DMAing directly to file (splice). And setting the immutable bit right away on start. Then once the capture is done (capture file recycled) the file becomes immutable. Such program is now broken. Who's fault is it? I'm totally not sure and maybe you are right. But have you made a survey of the majority of immutable uses, and are positive that the guys are not broken after this change? For me this is kind of scary. Yes I am known to be a SW coward ;-) Thanks Boaz