From patchwork Fri Aug 14 04:30:16 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 7012161 Return-Path: X-Original-To: patchwork-linux-fsdevel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork2.web.kernel.org (Postfix) with ESMTP id 9F4E7C05AC for ; Fri, 14 Aug 2015 04:37:12 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id B227820434 for ; Fri, 14 Aug 2015 04:37:11 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C559820431 for ; Fri, 14 Aug 2015 04:37:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752187AbbHNEhJ (ORCPT ); Fri, 14 Aug 2015 00:37:09 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:57523 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752068AbbHNEhI (ORCPT ); Fri, 14 Aug 2015 00:37:08 -0400 Received: from in01.mta.xmission.com ([166.70.13.51]) by out02.mta.xmission.com with esmtps (TLS1.2:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1ZQ6jr-0005WK-AJ; Thu, 13 Aug 2015 22:37:07 -0600 Received: from 67-3-205-173.omah.qwest.net ([67.3.205.173] helo=x220.int.ebiederm.org.xmission.com) by in01.mta.xmission.com with esmtpsa (TLS1.2:DHE_RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1ZQ6jp-0006TF-GD; Thu, 13 Aug 2015 22:37:07 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Linux Containers Cc: linux-fsdevel@vger.kernel.org, Al Viro , Andy Lutomirski , "Serge E. Hallyn" , Richard Weinberger , Andrey Vagin , Jann Horn , Willy Tarreau , Omar Sandoval , Miklos Szeredi , Linus Torvalds , "J. Bruce Fields" References: <871tncuaf6.fsf@x220.int.ebiederm.org> <87mw5xq7lt.fsf@x220.int.ebiederm.org> <87a8yqou41.fsf_-_@x220.int.ebiederm.org> <874moq9oyb.fsf_-_@x220.int.ebiederm.org> <871tfkawu9.fsf_-_@x220.int.ebiederm.org> <87egjk9i61.fsf_-_@x220.int.ebiederm.org> <20150810043637.GC14139@ZenIV.linux.org.uk> <877foymrwt.fsf@x220.int.ebiederm.org> <87wpwyjxwc.fsf_-_@x220.int.ebiederm.org> Date: Thu, 13 Aug 2015 23:30:16 -0500 In-Reply-To: <87wpwyjxwc.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Thu, 13 Aug 2015 23:29:23 -0500") Message-ID: <87r3n6jxuv.fsf_-_@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 X-XM-AID: U2FsdGVkX189oVY1b5RGtRtmUGovB8IiPxiH6eK+yQo= X-SA-Exim-Connect-IP: 67.3.205.173 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=ham version=3.3.1 X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Linux Containers X-Spam-Relay-Country: X-Spam-Timing: total 1335 ms - load_scoreonly_sql: 0.06 (0.0%), signal_user_changed: 7 (0.5%), b_tie_ro: 4.7 (0.4%), parse: 1.86 (0.1%), extract_message_metadata: 17 (1.3%), get_uri_detail_list: 1.80 (0.1%), tests_pri_-1000: 7 (0.5%), tests_pri_-950: 1.54 (0.1%), tests_pri_-900: 1.25 (0.1%), tests_pri_-400: 26 (2.0%), check_bayes: 25 (1.9%), b_tokenize: 7 (0.5%), b_tok_get_all: 9 (0.7%), b_comp_prob: 2.5 (0.2%), b_tok_touch_all: 3.6 (0.3%), b_finish: 0.94 (0.1%), tests_pri_0: 1260 (94.4%), tests_pri_500: 7 (0.5%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH review 1/8] dcache: Handle escaped paths in prepend_path X-SA-Exim-Version: 4.2.1 (built Wed, 24 Sep 2014 11:00:52 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) 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 A rename can result in a dentry that by walking up d_parent will never reach it's mnt_root. For lack of a better term I call this an escaped path. prepend_path is called by four different functions __d_path, d_absolute_path, d_path, and getcwd. __d_path only wants to see paths are connected to the root it passes in. So __d_path needs prepend_path to return an error. d_absolute_path similarly wants to see paths that are connected to some root. Escaped paths are not connected to any mnt_root so d_absolute_path needs prepend_path to return an error greater than 1. So escaped paths will be treated like paths on lazily unmounted mounts. getcwd needs to prepend "(unreachable)" so getcwd also needs prepend_path to return an error. d_path is the interesting hold out. d_path just wants to print something, and does not care about the weird cases. Which raises the question what should be printed? Given that / should result in -ENOENT I believe it is desirable for escaped paths to be printed as empty paths. As there are not really any meaninful path components when considered from the perspective of a mount tree. So tweak prepend_path to return an empty path with an new error code of 3 when it encounters an escaped path. Signed-off-by: "Eric W. Biederman" --- fs/dcache.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/fs/dcache.c b/fs/dcache.c index 7a3f3e5f9cea..f762e76e85cc 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2923,6 +2923,13 @@ restart: if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { struct mount *parent = ACCESS_ONCE(mnt->mnt_parent); + /* Escaped? */ + if (dentry != vfsmnt->mnt_root) { + bptr = *buffer; + blen = *buflen; + error = 3; + break; + } /* Global root? */ if (mnt != parent) { dentry = ACCESS_ONCE(mnt->mnt_mountpoint);