From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752044AbcFWTJA (ORCPT ); Thu, 23 Jun 2016 15:09:00 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:43075 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750919AbcFWTI5 (ORCPT ); Thu, 23 Jun 2016 15:08:57 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: "Michael Kerrisk \(man-pages\)" Cc: Oleg Nesterov , Jann Horn , James Morris , linux-man , Stephen Smalley , lkml , Kees Cook , linux-security-module , Linux API References: <87ziqewc3r.fsf@x220.int.ebiederm.org> <20160622215142.GA14751@redhat.com> Date: Thu, 23 Jun 2016 13:56:39 -0500 In-Reply-To: (Michael Kerrisk's message of "Thu, 23 Jun 2016 09:06:55 +0200") Message-ID: <871t3nka3c.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.5 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1bG9zi-0007Z4-51;;;mid=<871t3nka3c.fsf@x220.int.ebiederm.org>;;;hst=in01.mta.xmission.com;;;ip=67.3.204.119;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX19O/CTEF3NS2exead119JlBp6MLIFs+Ui8= X-SA-Exim-Connect-IP: 67.3.204.119 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.0 TVD_RCVD_IP Message was received from an IP address * 0.0 T_TM2_M_HEADER_IN_MSG BODY: No description available. * 0.8 BAYES_50 BODY: Bayes spam probability is 40 to 60% * [score: 0.5000] * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa06 1397; Body=1 Fuz1=1 Fuz2=1] * 0.2 T_XMDrugObfuBody_14 obfuscated drug references X-Spam-DCC: XMission; sa06 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;"Michael Kerrisk \(man-pages\)" X-Spam-Relay-Country: X-Spam-Timing: total 1251 ms - load_scoreonly_sql: 0.05 (0.0%), signal_user_changed: 3.5 (0.3%), b_tie_ro: 2.4 (0.2%), parse: 0.97 (0.1%), extract_message_metadata: 3.8 (0.3%), get_uri_detail_list: 1.68 (0.1%), tests_pri_-1000: 3.7 (0.3%), tests_pri_-950: 1.14 (0.1%), tests_pri_-900: 0.99 (0.1%), tests_pri_-400: 25 (2.0%), check_bayes: 24 (2.0%), b_tokenize: 8 (0.7%), b_tok_get_all: 7 (0.6%), b_comp_prob: 2.8 (0.2%), b_tok_touch_all: 3.6 (0.3%), b_finish: 0.96 (0.1%), tests_pri_0: 1195 (95.5%), check_dkim_signature: 0.53 (0.0%), check_dkim_adsp: 3.4 (0.3%), tests_pri_500: 3.3 (0.3%), rewrite_mail: 0.00 (0.0%) Subject: Re: Documenting ptrace access mode checking X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Thu, 05 May 2016 13:38:54 -0600) X-SA-Exim-Scanned: Yes (on in01.mta.xmission.com) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org "Michael Kerrisk (man-pages)" writes: > 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). Which are interesting in this respect as a bug in the implementation that is a security issue can and will be changed, even if userspace breaks. Breaking userspace is not desirable but when there is no other reasonable choice it will happen. Eric