From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934070AbbJIAkq (ORCPT ); Thu, 8 Oct 2015 20:40:46 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:35832 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933853AbbJIAjj (ORCPT ); Thu, 8 Oct 2015 20:39:39 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Al Viro" , "Eric W. Biederman" Date: Fri, 09 Oct 2015 01:12:27 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.2 030/107] dcache: Handle escaped paths in prepend_path In-Reply-To: X-SA-Exim-Connect-IP: 192.168.4.247 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 3.2.72-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: "Eric W. Biederman" commit cde93be45a8a90d8c264c776fab63487b5038a65 upstream. 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" Signed-off-by: Al Viro Signed-off-by: Ben Hutchings --- fs/dcache.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/fs/dcache.c b/fs/dcache.c index 8a3530067f03..46265f58b5b8 100644 --- a/fs/dcache.c +++ b/fs/dcache.c @@ -2452,6 +2452,8 @@ static int prepend_path(const struct path *path, { struct dentry *dentry = path->dentry; struct vfsmount *vfsmnt = path->mnt; + char *orig_buffer = *buffer; + int orig_len = *buflen; bool slash = false; int error = 0; @@ -2459,6 +2461,14 @@ static int prepend_path(const struct path *path, struct dentry * parent; if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) { + /* Escaped? */ + if (dentry != vfsmnt->mnt_root) { + *buffer = orig_buffer; + *buflen = orig_len; + slash = false; + error = 3; + goto global_root; + } /* Global root? */ if (vfsmnt->mnt_parent == vfsmnt) { goto global_root;