From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1427078AbdD2XZN (ORCPT ); Sat, 29 Apr 2017 19:25:13 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:46974 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1426209AbdD2XZG (ORCPT ); Sat, 29 Apr 2017 19:25:06 -0400 Date: Sun, 30 Apr 2017 00:25:04 +0100 From: Al Viro To: Andy Lutomirski Cc: Linux API , "linux-kernel@vger.kernel.org" , Linux FS Devel Subject: Re: new ...at() flag: AT_NO_JUMPS Message-ID: <20170429232504.GU29622@ZenIV.linux.org.uk> References: <20170429220414.GT29622@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Apr 29, 2017 at 04:17:18PM -0700, Andy Lutomirski wrote: > On Sat, Apr 29, 2017 at 3:04 PM, Al Viro wrote: > > New AT_... flag - AT_NO_JUMPS > > > > Semantics: pathname resolution must not involve > > * traversals of absolute symlinks > > * traversals of procfs-style symlinks > > * traversals of mountpoints (including bindings, referrals, etc.) > > * traversal of .. in the starting point of pathname resolution. > > Can you clarify this last one? I assume that ".." will be rejected, > but what about "a/../.."? How about "b" if b is a symlink to ".."? > How about "a/b" if a is a directory and b is a symlink to "../.."? All of those will be rejected - in each of those cases pathname traversal leads back into the starting point with .. being the next component to handle.