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=-9.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT autolearn=unavailable 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 9F8FFC3F2D1 for ; Sun, 1 Mar 2020 21:53:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 75422246BF for ; Sun, 1 Mar 2020 21:53:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727306AbgCAVxB (ORCPT ); Sun, 1 Mar 2020 16:53:01 -0500 Received: from zeniv.linux.org.uk ([195.92.253.2]:41710 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727146AbgCAVws (ORCPT ); Sun, 1 Mar 2020 16:52:48 -0500 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1j8WVz-003fPt-9D; Sun, 01 Mar 2020 21:52:47 +0000 From: Al Viro To: linux-fsdevel@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Linus Torvalds Subject: [RFC][PATCH v3 43/55] follow_dotdot{,_rcu}(): lift LOOKUP_BENEATH checks out of loop Date: Sun, 1 Mar 2020 21:52:28 +0000 Message-Id: <20200301215240.873899-43-viro@ZenIV.linux.org.uk> X-Mailer: git-send-email 2.24.1 In-Reply-To: <20200301215240.873899-1-viro@ZenIV.linux.org.uk> References: <20200301215125.GA873525@ZenIV.linux.org.uk> <20200301215240.873899-1-viro@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Al Viro Behaviour change: LOOKUP_BENEATH lookup of .. in absolute root yields an error even if it's not the process' root. That's possible only if you'd managed to escape chroot jail by way of procfs symlinks, but IMO the resulting behaviour is not worse - more consistent and easier to describe: ".." in root is "stay where you are", uness LOOKUP_BENEATH has been given, in which case it's "fail with EXDEV". Signed-off-by: Al Viro --- fs/namei.c | 20 ++++++++++---------- 1 file changed, 10 insertions(+), 10 deletions(-) diff --git a/fs/namei.c b/fs/namei.c index c307bf7cbaa1..be756aa32240 100644 --- a/fs/namei.c +++ b/fs/namei.c @@ -1370,11 +1370,8 @@ static int follow_dotdot_rcu(struct nameidata *nd) unsigned seq; while (1) { - if (path_equal(&nd->path, &nd->root)) { - if (unlikely(nd->flags & LOOKUP_BENEATH)) - return -ECHILD; + if (path_equal(&nd->path, &nd->root)) break; - } if (nd->path.dentry != nd->path.mnt->mnt_root) { struct dentry *old = nd->path.dentry; @@ -1405,7 +1402,10 @@ static int follow_dotdot_rcu(struct nameidata *nd) nd->seq = seq; } } - if (likely(parent)) { + if (unlikely(!parent)) { + if (unlikely(nd->flags & LOOKUP_BENEATH)) + return -ECHILD; + } else { nd->path.dentry = parent; nd->seq = seq; } @@ -1447,11 +1447,8 @@ static int follow_dotdot(struct nameidata *nd) { struct dentry *parent = NULL; while (1) { - if (path_equal(&nd->path, &nd->root)) { - if (unlikely(nd->flags & LOOKUP_BENEATH)) - return -EXDEV; + if (path_equal(&nd->path, &nd->root)) break; - } if (nd->path.dentry != nd->path.mnt->mnt_root) { /* rare case of legitimate dget_parent()... */ parent = dget_parent(nd->path.dentry); @@ -1466,7 +1463,10 @@ static int follow_dotdot(struct nameidata *nd) if (unlikely(nd->flags & LOOKUP_NO_XDEV)) return -EXDEV; } - if (likely(parent)) { + if (unlikely(!parent)) { + if (unlikely(nd->flags & LOOKUP_BENEATH)) + return -EXDEV; + } else { dput(nd->path.dentry); nd->path.dentry = parent; } -- 2.11.0