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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED autolearn=ham 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 4A551C43441 for ; Mon, 26 Nov 2018 12:57:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 147C120817 for ; Mon, 26 Nov 2018 12:57:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 147C120817 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=huawei.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726964AbeKZXvT (ORCPT ); Mon, 26 Nov 2018 18:51:19 -0500 Received: from lhrrgout.huawei.com ([185.176.76.210]:32782 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726276AbeKZXvS (ORCPT ); Mon, 26 Nov 2018 18:51:18 -0500 Received: from LHREML712-CAH.china.huawei.com (unknown [172.18.7.108]) by Forcepoint Email with ESMTP id D41FD2EB36DB4; Mon, 26 Nov 2018 12:57:11 +0000 (GMT) Received: from [10.204.65.144] (10.204.65.144) by smtpsuk.huawei.com (10.201.108.35) with Microsoft SMTP Server (TLS) id 14.3.408.0; Mon, 26 Nov 2018 12:57:06 +0000 Subject: Re: [RFC][PATCH] fs: set xattrs in initramfs from regular files To: Rob Landley , CC: , , , , , , , , , , , , References: <20181122154942.18262-1-roberto.sassu@huawei.com> <7f2b0288-a173-e2bb-70ee-d552610bfc1e@landley.net> From: Roberto Sassu Message-ID: Date: Mon, 26 Nov 2018 13:56:58 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <7f2b0288-a173-e2bb-70ee-d552610bfc1e@landley.net> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.204.65.144] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/23/2018 9:21 PM, Rob Landley wrote: > On 11/22/18 9:49 AM, Roberto Sassu wrote: >> Although rootfs (tmpfs) supports xattrs, they are not set due to the >> limitation of the cpio format. A new format called 'newcx' was proposed to >> overcome this limitation. > > I got email about that format the day before you posted this, by the way. > >> However, it looks like that adding a new format is not simple: 15 kernel >> patches; user space tools must support the new format; mistakes made in the >> past should be avoided; it is unclear whether the kernel should switch from >> cpio to tar. > > The kernel _can't_ switch from cpio to tar without breaking backwards > compatability, it could only add tar as a second format it supported (remember > cpio images can be sideloaded so a new rootfs can be used with an existing > initramfs, plus existing build systems generate them and would still need to if > they wanted to keep supporting older kernels), and then once you've got two > formats somebody will propose zip support, and let's just not go there please. > > The changes to the userspace tools are trivial (I say that as the maintainer of > toybox, which has a cpio). The argument was about things like 64 bit timestamps > (y2038 problem), nanosecond support, sparse files, etc. And I think the argument > had largely died down? > > Keep in mind the squashfs guy spent 5 years trying to get his filesystem merged > (https://lwn.net/Articles/563578/), I spent several years trying to get my perl > removal patch merged (and only work up the enthusiasm to resubmit > http://lists.busybox.net/pipermail/buildroot/2015-March/123385.html > https://patchwork.kernel.org/patch/9193529/ https://lkml.org/lkml/2017/9/13/651 > about once a year because dealing with linux-kernel is just no fun for hobbyists > anymore). > >> The aim of this patch is to provide the same functionality without >> introducing a new format. The value of xattrs is placed in regular files >> having the same file name as the files xattrs are added to, plus a >> separator and the xattr name (.xattr-). > > I think you're solving the wrong problem, but that's just my opinion. Instead of iterating over rootfs, would it be better to detect files with extended attributes (from the file name) when the cpio image is parsed by the kernel, and call sys_lsetxattr() in do_copy()? This part can be turned on by introducing a new type in the existing format (if possible). The impact of this alternative is very low, and LSMs/IMA would be able, with minimum effort, to enforce policies on files in the initial ram disk. Roberto > Rob > -- HUAWEI TECHNOLOGIES Duesseldorf GmbH, HRB 56063 Managing Director: Bo PENG, Jian LI, Yanli SHI