From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933298AbbHLBYj (ORCPT ); Tue, 11 Aug 2015 21:24:39 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:51551 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932755AbbHLBYi (ORCPT ); Tue, 11 Aug 2015 21:24:38 -0400 From: ebiederm@xmission.com (Eric W. Biederman) To: Oleg Nesterov Cc: "Kirill A. Shutemov" , Andrew Morton , Kees Cook , David Howells , linux-kernel@vger.kernel.org, Peter Zijlstra , Ingo Molnar , "Kirill A. Shutemov" , Rik van Riel , Vladimir Davydov , Ricky Zhou , Julien Tinnes References: <20150728171500.GA2871@www.outflux.net> <20150728143504.5aa996ba5955522a19c2d5f1@linux-foundation.org> <20150728221111.GA23391@node.dhcp.inet.fi> <20150805172356.GA20490@redhat.com> <87wpx9sjhq.fsf@x220.int.ebiederm.org> <87614tr2jd.fsf@x220.int.ebiederm.org> <20150806130629.GA4728@redhat.com> <20150806134426.GA6843@redhat.com> Date: Tue, 11 Aug 2015 20:17:48 -0500 In-Reply-To: <20150806134426.GA6843@redhat.com> (Oleg Nesterov's message of "Thu, 6 Aug 2015 15:44:26 +0200") Message-ID: <87egj9cnk3.fsf@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.3 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-AID: U2FsdGVkX18OJv5i69luLDItIBcILDHlhwDcpBMTNZ4= X-SA-Exim-Connect-IP: 67.3.205.173 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * 0.7 XMSubLong Long Subject * 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 * [sa01 1397; Body=1 Fuz1=1 Fuz2=1] * 0.0 T_TooManySym_01 4+ unique symbols in subject X-Spam-DCC: XMission; sa01 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Oleg Nesterov X-Spam-Relay-Country: X-Spam-Timing: total 505 ms - load_scoreonly_sql: 0.06 (0.0%), signal_user_changed: 4.3 (0.8%), b_tie_ro: 2.9 (0.6%), parse: 1.23 (0.2%), extract_message_metadata: 4.2 (0.8%), get_uri_detail_list: 1.68 (0.3%), tests_pri_-1000: 7 (1.4%), tests_pri_-950: 2.0 (0.4%), tests_pri_-900: 1.74 (0.3%), tests_pri_-400: 30 (6.0%), check_bayes: 28 (5.6%), b_tokenize: 11 (2.1%), b_tok_get_all: 7 (1.5%), b_comp_prob: 3.7 (0.7%), b_tok_touch_all: 3.3 (0.7%), b_finish: 0.92 (0.2%), tests_pri_0: 426 (84.4%), tests_pri_500: 6 (1.3%), rewrite_mail: 0.00 (0.0%) Subject: Re: [PATCH] user_ns: use correct check for single-threadedness X-Spam-Flag: No X-SA-Exim-Version: 4.2.1 (built Wed, 24 Sep 2014 11:00:52 -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 Oleg Nesterov writes: > On 08/06, Oleg Nesterov wrote: >> >> On 08/05, Eric W. Biederman wrote: >> > >> > So I have to ask. >> >> I hope you are asking someone else, not me ;) I never understood what >> exactly we try to restrict and why. >> >> > Is it possible to rework these checks such that we >> > look at the sighand struct and signal sharing handling sharing instead >> > of the count on the mm_struct? >> >> Then why we can't simply check thread_group_empty() == T ? Why should we >> worry about CLONE_SIGHAND at all? > > The same for clone() actually... I forgot why we decided to check > CLONE_SIGHAND, iirc I suggested CLONE_THREAD initially then we switched > to CLONE_SIGHAND "just in case", to make it as strict as possible. I do agree that making the test be for CLONE_THREAD is safe, makes sense, and is less confusing than what we have now.x > How about the patch below? > > (note that the "or parent" part of the comment is wrong in any case). It was correct. You failed to removed it when you removed CLONE_PARENT from that test. Eric