From patchwork Fri Jun 21 23:56:50 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 11010927 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 821ED76 for ; Fri, 21 Jun 2019 23:58:48 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 74AF02870D for ; Fri, 21 Jun 2019 23:58:48 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 681A828BAD; Fri, 21 Jun 2019 23:58:48 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 0A4422870D for ; Fri, 21 Jun 2019 23:58:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726661AbfFUX6m (ORCPT ); Fri, 21 Jun 2019 19:58:42 -0400 Received: from userp2120.oracle.com ([156.151.31.85]:36930 "EHLO userp2120.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726636AbfFUX6g (ORCPT ); Fri, 21 Jun 2019 19:58:36 -0400 Received: from pps.filterd (userp2120.oracle.com [127.0.0.1]) by userp2120.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x5LNt5Xd059348; Fri, 21 Jun 2019 23:56:58 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : from : to : cc : date : message-id : mime-version : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=fawPQY/UISfSH6DvrztcWabWXm47TtXieQJWSELxOKQ=; b=VYwNeL6ibPXVTEVoRkPUTgHJCT2wzrlt5vhgzdSSWt3OQjBNDlvSlcMAel/+5/qiR1of h2fH3k9W374Ek5nhUZh18oW2OLVU8FOtFCEtIVH579hK6M1M54/APh5/t3SUPGKy7t9V zr4flVMsY+8M+/9Er2kArmiUZJYRUJeMUa6Z3FeKdWFkw5uKS18otDCNc6AjwWI6ftkm Qf7O4LpTTnOL9WPw64vBXu6TFLd4bcXU3WYyHNH2O8UezLzZ+yDrtb1pzL64XMboTNNv P0vzfKCxcw4dY1NwEQj5N4JcCQ2pFTiMWGgyRXLO/ijggAoaKJ7wtQ0X968LtP9NJ5HD 2A== Received: from aserp3030.oracle.com (aserp3030.oracle.com [141.146.126.71]) by userp2120.oracle.com with ESMTP id 2t7809rqup-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 21 Jun 2019 23:56:57 +0000 Received: from pps.filterd (aserp3030.oracle.com [127.0.0.1]) by aserp3030.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x5LNtKaA167994; Fri, 21 Jun 2019 23:56:57 GMT Received: from pps.reinject (localhost [127.0.0.1]) by aserp3030.oracle.com with ESMTP id 2t7rdy0604-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Fri, 21 Jun 2019 23:56:57 +0000 Received: from aserp3030.oracle.com (aserp3030.oracle.com [127.0.0.1]) by pps.reinject (8.16.0.27/8.16.0.27) with SMTP id x5LNuue9170472; Fri, 21 Jun 2019 23:56:56 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserp3030.oracle.com with ESMTP id 2t7rdy05yy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Fri, 21 Jun 2019 23:56:56 +0000 Received: from abhmp0002.oracle.com (abhmp0002.oracle.com [141.146.116.8]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x5LNurk8019074; Fri, 21 Jun 2019 23:56:53 GMT Received: from localhost (/10.159.131.214) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Fri, 21 Jun 2019 16:56:53 -0700 Subject: [PATCH v4 0/7] vfs: make immutable files actually immutable From: "Darrick J. Wong" To: matthew.garrett@nebula.com, yuchao0@huawei.com, tytso@mit.edu, darrick.wong@oracle.com, ard.biesheuvel@linaro.org, josef@toxicpanda.com, 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 Date: Fri, 21 Jun 2019 16:56:50 -0700 Message-ID: <156116141046.1664939.11424021489724835645.stgit@magnolia> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=nai engine=6000 definitions=9295 signatures=668687 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1906210182 Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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. Therefore, add immutability checks to the relevant VFS functions, then refactor the SETFLAGS and FSSETXATTR implementations to use common argument checking functions so that we can then force pagefaults on all the file data when setting immutability. Note that various distro manpages points out the inconsistent behavior of the various Linux filesystems w.r.t. immutable. This fixes all that. I also discovered that userspace programs can write and create writable memory mappings to active swap files. This is extremely bad because this allows anyone with write privileges to corrupt system memory. The final patch in this series closes off that hole, at least for swap files. If you're going to start using this mess, you probably ought to just pull from my git trees, which are linked below. This has been lightly tested with fstests. Enjoy! Comments and questions are, as always, welcome. --D kernel git tree: https://git.kernel.org/cgit/linux/kernel/git/djwong/xfs-linux.git/log/?h=immutable-files fstests git tree: https://git.kernel.org/cgit/linux/kernel/git/djwong/xfstests-dev.git/log/?h=immutable-files