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=-3.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_PASS 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 B6C67ECDE30 for ; Wed, 17 Oct 2018 14:36:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 706F520658 for ; Wed, 17 Oct 2018 14:36:06 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 706F520658 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=xmission.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 S1727485AbeJQWcD convert rfc822-to-8bit (ORCPT ); Wed, 17 Oct 2018 18:32:03 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:54666 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727040AbeJQWcD (ORCPT ); Wed, 17 Oct 2018 18:32:03 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1gCmvb-0000oe-W0; Wed, 17 Oct 2018 08:36:04 -0600 Received: from 67-3-154-154.omah.qwest.net ([67.3.154.154] helo=x220.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.87) (envelope-from ) id 1gCmvb-0002fB-0g; Wed, 17 Oct 2018 08:36:03 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Alan Jenkins Cc: David Howells , Al Viro , linux-api@vger.kernel.org, torvalds@linux-foundation.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mszeredi@redhat.com References: <19866.1539782101@warthog.procyon.org.uk> <68a2107f-bf70-055b-86cf-1ba2ba9422bf@gmail.com> <153754740781.17872.7869536526927736855.stgit@warthog.procyon.org.uk> <153754766004.17872.9829232103614083565.stgit@warthog.procyon.org.uk> <9b8bf436-65de-13b9-0002-0479d11c18ca@gmail.com> <20181013061141.GR32577@ZenIV.linux.org.uk> <28710.1539782412@warthog.procyon.org.uk> Date: Wed, 17 Oct 2018 09:35:45 -0500 In-Reply-To: (Alan Jenkins's message of "Wed, 17 Oct 2018 15:31:26 +0100") Message-ID: <87woqgiqta.fsf@xmission.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8BIT X-XM-SPF: eid=1gCmvb-0002fB-0g;;;mid=<87woqgiqta.fsf@xmission.com>;;;hst=in01.mta.xmission.com;;;ip=67.3.154.154;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19hcb5RQKjAH6x0dAjbhxUx+4sBQrfVGB4= X-SA-Exim-Connect-IP: 67.3.154.154 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration [ver #12] X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Alan Jenkins writes: > On 17/10/2018 14:20, David Howells wrote: >> David Howells wrote: >> >>> I should probably check that the picked point is actually a mountpoint. >> The root of the mount object at the path specified, that is, perhaps with >> something like the attached. >> >> David > > > I agree.  I'm happy to see this is using the same check as do_remount(). > > > * change filesystem flags. dir should be a physical root of filesystem. > * If you've mounted a non-root directory somewhere and want to do remount > * on it - tough luck. > */ Davids check will work for bind mounts as well. It just won't work it just won't work for files or subdirectories of some mountpoint. Eric >> --- >> diff --git a/fs/fsopen.c b/fs/fsopen.c >> index f673e93ac456..aaaaa17a233c 100644 >> --- a/fs/fsopen.c >> +++ b/fs/fsopen.c >> @@ -186,6 +186,10 @@ SYSCALL_DEFINE3(fspick, int, dfd, const char __user *, path, unsigned int, flags >> if (ret < 0) >> goto err; >> + ret = -EINVAL; >> + if (target.mnt->mnt_root != target.dentry) >> + goto err_path; >> + >> fc = vfs_new_fs_context(target.dentry->d_sb->s_type, target.dentry, >> 0, 0, FS_CONTEXT_FOR_RECONFIGURE); >> if (IS_ERR(fc)) { >>