Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753847AbaBCVo0 (ORCPT ); Mon, 3 Feb 2014 16:44:26 -0500 Received: from mail-ve0-f172.google.com ([209.85.128.172]:56564 "EHLO mail-ve0-f172.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753431AbaBCVoX (ORCPT ); Mon, 3 Feb 2014 16:44:23 -0500 MIME-Version: 1.0 In-Reply-To: <20140203213926.GA10323@ZenIV.linux.org.uk> References: <1391013467-7598-1-git-send-email-ilya.dryomov@inktank.com> <20140130075421.GA10050@infradead.org> <20140203102943.GF11829@infradead.org> <20140203211955.GY10323@ZenIV.linux.org.uk> <20140203213926.GA10323@ZenIV.linux.org.uk> Date: Mon, 3 Feb 2014 13:44:22 -0800 X-Google-Sender-Auth: E_GTp_YUqNv4N_2gz0DMC-ASsqc Message-ID: Subject: Re: [PATCH v2] ceph: fix posix ACL hooks From: Linus Torvalds To: Al Viro Cc: Christoph Hellwig , Ilya Dryomov , Sage Weil , Dave Jones , Linux Kernel Mailing List , ceph-devel@vger.kernel.org, linux-fsdevel , Guangliang Zhao , Li Wang , zheng.z.yan@intel.com Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 3, 2014 at 1:39 PM, Al Viro wrote: > > If we really have hardlinks, the result of permission check would better > be a function of inode itself - as in, "if it gives different results > for two pathnames reachable for the same user, we have a bug". No. You're wrong. EVEN ON A UNIX FILESYSTEM THE PATH IS MEANINGFUL. Do this: create a hardlink in two different directories. Make the *directory* permissions for one of the directories be something you cannot traverse. Now try to check the permissions of the *same* inode through those two paths. Notice how you get *different* results. Really. Now, imagine that you are doing the same thing over a network. On the server, there may be a single inode for the file, but when the client gives the server a pathname, the two pathnames to that single inode ARE NOT EQUIVALENT. And the fact is, filesystems with hardlinks and path-name-based operations do exist. cifs with the unix extensions is one of them. Al, face it, you're wrong this time. Linus -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/