From patchwork Wed Apr 17 19:04:33 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: 10905971 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 044BD17E6 for ; Wed, 17 Apr 2019 19:06:41 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id E799928B87 for ; Wed, 17 Apr 2019 19:06:40 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id DC68C28B96; Wed, 17 Apr 2019 19:06:40 +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=-5.5 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, SUSPICIOUS_RECIPS,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 7612D28B8A for ; Wed, 17 Apr 2019 19:06:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1733269AbfDQTGi (ORCPT ); Wed, 17 Apr 2019 15:06:38 -0400 Received: from aserp2130.oracle.com ([141.146.126.79]:37830 "EHLO aserp2130.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730230AbfDQTGi (ORCPT ); Wed, 17 Apr 2019 15:06:38 -0400 Received: from pps.filterd (aserp2130.oracle.com [127.0.0.1]) by aserp2130.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x3HIwrW0174911; Wed, 17 Apr 2019 19:06:36 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=subject : from : to : cc : date : message-id : in-reply-to : references : mime-version : content-type : content-transfer-encoding; s=corp-2018-07-02; bh=JouHYqapC+Bru3b7LvDckRkkxunv72G7Ij9fwNIVhtw=; b=sYhTtogV2rz0CQ7WtQZBxg27VjT2c0iYvfnb7MkAJHjwYWyrFXX6d2yTmAznDmyilqJB d9OepAaFTrcZi9wpBI7rBESJRoaT0WSSYhAUssNFj/G2xlcBkOYOCjddOG1LIfQtQ4qz PTMnFG8X0NjYd7F982V9yU1WjX/KOcluZaBD2LzIqWcHZsy4njOrTS32V6UrEAPZ6z7T oaM12PSyqVObWxMFI7ckyHglKDXbpbSsY8pON5zwmFRPj93BLpv3AAq6Hj5qYi76xbTF LImlFac+FuXVRvr6GL7FGrEWHWE49GT1YxhLtDrfYyIZwStbi1ZswjmAyxCQlYdDb2j/ HQ== Received: from userp3020.oracle.com (userp3020.oracle.com [156.151.31.79]) by aserp2130.oracle.com with ESMTP id 2ru59dcxbv-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 17 Apr 2019 19:06:35 +0000 Received: from pps.filterd (userp3020.oracle.com [127.0.0.1]) by userp3020.oracle.com (8.16.0.27/8.16.0.27) with SMTP id x3HJ4ScB119486; Wed, 17 Apr 2019 19:04:35 GMT Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by userp3020.oracle.com with ESMTP id 2rubq744gy-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Wed, 17 Apr 2019 19:04:34 +0000 Received: from abhmp0015.oracle.com (abhmp0015.oracle.com [141.146.116.21]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x3HJ4YpM020984; Wed, 17 Apr 2019 19:04:34 GMT Received: from localhost (/67.169.218.210) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 17 Apr 2019 12:04:34 -0700 Subject: [PATCH 1/8] mm/fs: don't allow writes to immutable files From: "Darrick J. Wong" To: darrick.wong@oracle.com Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, linux-mm@kvack.org Date: Wed, 17 Apr 2019 12:04:33 -0700 Message-ID: <155552787330.20411.11893581890744963309.stgit@magnolia> In-Reply-To: <155552786671.20411.6442426840435740050.stgit@magnolia> References: <155552786671.20411.6442426840435740050.stgit@magnolia> User-Agent: StGit/0.17.1-dirty MIME-Version: 1.0 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9230 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 suspectscore=1 malwarescore=0 phishscore=0 bulkscore=0 spamscore=0 mlxscore=0 mlxlogscore=265 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904170125 X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9230 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=1 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=292 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1904170125 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 From: Darrick J. Wong The chattr manpage has this to say about immutable 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." Once the flag is set, it is enforced for quite a few file operations, such as fallocate, fpunch, fzero, rm, touch, open, etc. However, we don't check for immutability when doing a write(), a PROT_WRITE mmap(), a truncate(), or a write to a previously established mmap. If a program has an open write fd to a file that the administrator subsequently marks immutable, the program still can change the file contents. Weird! The ability to write to an immutable file does not follow the manpage promise that immutable files cannot be modified. Worse yet it's inconsistent with the behavior of other syscalls which don't allow modifications of immutable files. Therefore, add the necessary checks to make the write, mmap, and truncate behavior consistent with what the manpage says and consistent with other syscalls on filesystems which support IMMUTABLE. Signed-off-by: Darrick J. Wong --- fs/attr.c | 13 ++++++------- mm/filemap.c | 3 +++ mm/memory.c | 3 +++ mm/mmap.c | 8 ++++++-- 4 files changed, 18 insertions(+), 9 deletions(-) diff --git a/fs/attr.c b/fs/attr.c index d22e8187477f..1fcfdcc5b367 100644 --- a/fs/attr.c +++ b/fs/attr.c @@ -233,19 +233,18 @@ int notify_change(struct dentry * dentry, struct iattr * attr, struct inode **de WARN_ON_ONCE(!inode_is_locked(inode)); - if (ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) { - if (IS_IMMUTABLE(inode) || IS_APPEND(inode)) - return -EPERM; - } + if (IS_IMMUTABLE(inode)) + return -EPERM; + + if ((ia_valid & (ATTR_MODE | ATTR_UID | ATTR_GID | ATTR_TIMES_SET)) && + IS_APPEND(inode)) + return -EPERM; /* * If utimes(2) and friends are called with times == NULL (or both * times are UTIME_NOW), then we need to check for write permission */ if (ia_valid & ATTR_TOUCH) { - if (IS_IMMUTABLE(inode)) - return -EPERM; - if (!inode_owner_or_capable(inode)) { error = inode_permission(inode, MAY_WRITE); if (error) diff --git a/mm/filemap.c b/mm/filemap.c index d78f577baef2..9fed698f4c63 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -3033,6 +3033,9 @@ inline ssize_t generic_write_checks(struct kiocb *iocb, struct iov_iter *from) loff_t count; int ret; + if (IS_IMMUTABLE(inode)) + return -EPERM; + if (!iov_iter_count(from)) return 0; diff --git a/mm/memory.c b/mm/memory.c index ab650c21bccd..dfd5eba278d6 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -2149,6 +2149,9 @@ static vm_fault_t do_page_mkwrite(struct vm_fault *vmf) vmf->flags = FAULT_FLAG_WRITE|FAULT_FLAG_MKWRITE; + if (vmf->vma->vm_file && IS_IMMUTABLE(file_inode(vmf->vma->vm_file))) + return VM_FAULT_SIGBUS; + ret = vmf->vma->vm_ops->page_mkwrite(vmf); /* Restore original flags so that caller is not surprised */ vmf->flags = old_flags; diff --git a/mm/mmap.c b/mm/mmap.c index 41eb48d9b527..697a101bda59 100644 --- a/mm/mmap.c +++ b/mm/mmap.c @@ -1481,8 +1481,12 @@ unsigned long do_mmap(struct file *file, unsigned long addr, case MAP_SHARED_VALIDATE: if (flags & ~flags_mask) return -EOPNOTSUPP; - if ((prot&PROT_WRITE) && !(file->f_mode&FMODE_WRITE)) - return -EACCES; + if (prot & PROT_WRITE) { + if (!(file->f_mode & FMODE_WRITE)) + return -EACCES; + if (IS_IMMUTABLE(file_inode(file))) + return -EPERM; + } /* * Make sure we don't allow writing to an append-only