From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751734AbcFWHHC (ORCPT ); Thu, 23 Jun 2016 03:07:02 -0400 Received: from mail-wm0-f49.google.com ([74.125.82.49]:37773 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751241AbcFWHG7 (ORCPT ); Thu, 23 Jun 2016 03:06:59 -0400 Subject: Re: Documenting ptrace access mode checking To: Oleg Nesterov , "Eric W. Biederman" References: <87ziqewc3r.fsf@x220.int.ebiederm.org> <20160622215142.GA14751@redhat.com> Cc: mtk.manpages@gmail.com, Jann Horn , James Morris , linux-man , Stephen Smalley , lkml , Kees Cook , linux-security-module , Linux API From: "Michael Kerrisk (man-pages)" Message-ID: Date: Thu, 23 Jun 2016 09:06:55 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.1.0 MIME-Version: 1.0 In-Reply-To: <20160622215142.GA14751@redhat.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Oleg, On 06/22/2016 11:51 PM, Oleg Nesterov wrote: > On 06/21, Eric W. Biederman wrote: >> >> Adding Oleg just because he seems to do most of the ptrace related >> maintenance these days. > > so I have to admit that I never even tried to actually understand > ptrace_may_access ;) > >> We certainly need something that gives a high level view so people >> reading the man page can know what to expect. If you get down into the >> weeds we run the danger of people beginning to think they can depend >> upon bugs in the implementation. > > Personally I agree. I think "man ptrace" shouldn't not tell too much > about kernel internals. See my other replies on this topic. Somehow, we need a way of describing the behavior that user-space sees. I think it's inevitable that that means talking about what;s going on "under the hood". Regarding Eric's point that "we run the danger of people beginning to think they can depend upon bugs in the implementation": when it comes to breaking the ABI, the presence or absence of documentation doesn't save us on that point (Linus has a few times made his position wrt to documentation clear). Cheers, Michael -- Michael Kerrisk Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/ Linux/UNIX System Programming Training: http://man7.org/training/