Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753522AbcDSX3S (ORCPT ); Tue, 19 Apr 2016 19:29:18 -0400 Received: from mail-io0-f196.google.com ([209.85.223.196]:34390 "EHLO mail-io0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751791AbcDSX3R (ORCPT ); Tue, 19 Apr 2016 19:29:17 -0400 MIME-Version: 1.0 In-Reply-To: <8737qhpifz.fsf@x220.int.ebiederm.org> References: <877ffyzy1j.fsf_-_@x220.int.ebiederm.org> <1460734532-20134-1-git-send-email-ebiederm@xmission.com> <1460734532-20134-14-git-send-email-ebiederm@xmission.com> <8737qhpifz.fsf@x220.int.ebiederm.org> Date: Tue, 19 Apr 2016 16:29:16 -0700 X-Google-Sender-Auth: If_RJZ-HUYxvWqqdPK2MnfxJ-ZY Message-ID: Subject: Re: [PATCH 14/16] vfs: Implement mount_super_once From: Linus Torvalds To: "Eric W. Biederman" Cc: "H. Peter Anvin" , Andy Lutomirski , security@debian.org, "security@kernel.org" , Al Viro , "security@ubuntu.com >> security" , Peter Hurley , Serge Hallyn , Willy Tarreau , Aurelien Jarno , One Thousand Gnomes , Jann Horn , Greg KH , Linux Kernel Mailing List , Jiri Slaby , Florian Weimer Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1497 Lines: 38 On Tue, Apr 19, 2016 at 11:22 AM, Eric W. Biederman wrote: > Linus Torvalds writes: >> >> No. >> >> We want to get *rid* of the idiotic "primary instance" crap. > > That is actually pretty much the opposite of what you said last time, > but having looked at the cost to maintian a "primary instance" notion > and what will break if we don't I am happy to remove such a notion > from devpts. No, it's what I said last time too, but there may have been an misunderstanding. I _violently_ oppose the stupid DEVPTS_MULTIPLE_INSTANCES config option. But I do _not_ oppose it because I want to have that "primary instance" cap. Quite the reverse. I oppose it because the *option* is stupid, and we should not have such an option. The kernel should always do multiple instances. There should never _ever_ be a "single instance" option, although obviously if you were to do a bind-mount of devpts, the bound mount would be the same instance. But if you do two separate mounts, they should alwats be separate insnaces. So what I want to fix is the crazy "that doesn't work" problem with Ubuntu or CentOS (or whatever distro it was) breaking, because /dev/ptmx ends up pointing to the *wrong* instance. This is literally why I think /dev/ptmx should just look up /dev/pts - simply to get rid of that idiotic special instance. It should not exist. It should not exist in the kernel, and it shouldn't exist in user space. Linus