From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BD211C10F29 for ; Tue, 17 Mar 2020 08:58:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 7A534206EC for ; Tue, 17 Mar 2020 08:58:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7A534206EC Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=virtuozzo.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 216906B0006; Tue, 17 Mar 2020 04:58:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1EE0E6B0007; Tue, 17 Mar 2020 04:58:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0DCDF6B0008; Tue, 17 Mar 2020 04:58:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0046.hostedemail.com [216.40.44.46]) by kanga.kvack.org (Postfix) with ESMTP id E7CCB6B0006 for ; Tue, 17 Mar 2020 04:58:08 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay01.hostedemail.com (Postfix) with ESMTP id BB80D180AD815 for ; Tue, 17 Mar 2020 08:58:08 +0000 (UTC) X-FDA: 76604252256.14.ink72_4715162938604 X-HE-Tag: ink72_4715162938604 X-Filterd-Recvd-Size: 8234 Received: from relay.sw.ru (relay.sw.ru [185.231.240.75]) by imf39.hostedemail.com (Postfix) with ESMTP for ; Tue, 17 Mar 2020 08:58:08 +0000 (UTC) Received: from [192.168.15.225] by relay.sw.ru with esmtp (Exim 4.92.3) (envelope-from ) id 1jE832-0003KS-Rn; Tue, 17 Mar 2020 11:58:05 +0300 Subject: Re: [PATCH v2 5/5] exec: Add a exec_update_mutex to replace cred_guard_mutex To: Bernd Edlinger , "Eric W. Biederman" Cc: Christian Brauner , Kees Cook , Jann Horn , Jonathan Corbet , Alexander Viro , Andrew Morton , Alexey Dobriyan , Thomas Gleixner , Oleg Nesterov , Frederic Weisbecker , Andrei Vagin , Ingo Molnar , "Peter Zijlstra (Intel)" , Yuyang Du , David Hildenbrand , Sebastian Andrzej Siewior , Anshuman Khandual , David Howells , James Morris , Greg Kroah-Hartman , Shakeel Butt , Jason Gunthorpe , Christian Kellner , Andrea Arcangeli , Aleksa Sarai , "Dmitry V. Levin" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "stable@vger.kernel.org" , "linux-api@vger.kernel.org" References: <87r1y8dqqz.fsf@x220.int.ebiederm.org> <87tv32cxmf.fsf_-_@x220.int.ebiederm.org> <87v9ne5y4y.fsf_-_@x220.int.ebiederm.org> <87zhcq4jdj.fsf_-_@x220.int.ebiederm.org> <87d09hn4kt.fsf@x220.int.ebiederm.org> <87lfo5lju6.fsf@x220.int.ebiederm.org> <6002ac56-025a-d50f-e89d-1bf42a072323@virtuozzo.com> From: Kirill Tkhai Message-ID: <68528401-58ff-c335-a752-00ebaa433e02@virtuozzo.com> Date: Tue, 17 Mar 2020 11:58:04 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 14.03.2020 13:02, Bernd Edlinger wrote: > On 3/14/20 10:57 AM, Bernd Edlinger wrote: >> On 3/13/20 10:13 AM, Kirill Tkhai wrote: >>> >>> Despite this should fix the problem, this looks like a broken puzzle. >>> >>> We can't use bprm->cred as an identifier whether the mutex was locked or not. >>> We can check for bprm->cred in regard to cred_guard_mutex, because of there is >>> strong rule: "cred_guard_mutex is becomes locked together with bprm->cred assignment >>> (see prepare_bprm_creds()), and it becomes unlocked together with bprm->cred zeroing". >>> Take attention on modularity of all this: there is no dependencies between anything else. >>> >>> In regard to newly introduced exec_update_mutex, your fix and source patch way look like >>> an obfuscation. The mutex becomes deadly glued to unrelated bprm->cred and bprm->mm, >>> and this introduces the problems in the future modifications and support of all involved >>> entities. If someone wants to move some functions in relation to each other, there will >>> be a pain, and this person will have to go again the same dependencies and bug way, >>> Eric stepped on in the original patch. >>> >> >> Okay, yes, valid points you make, thanks. >> I just wanted to understand what was exactly wrong with this patch, >> since the failure mode looked a lot like it was failing because of >> something clobbering the data unexpectedly. >> >> >> So I have posted a few updated patch for the failed one here: >> >> [PATCH v3 5/5] exec: Add a exec_update_mutex to replace cred_guard_mutex >> [PATCH] pidfd: Use new infrastructure to fix deadlocks in execve >> >> which replaces these: >> [PATCH v2 5/5] exec: Add a exec_update_mutex to replace cred_guard_mutex >> https://lore.kernel.org/lkml/87zhcq4jdj.fsf_-_@x220.int.ebiederm.org/ >> >> [PATCH] pidfd: Stop taking cred_guard_mutex >> https://lore.kernel.org/lkml/87wo7svy96.fsf_-_@x220.int.ebiederm.org/ >> >> >> and a new patch series to fix deadlock in ptrace_attach and update doc: >> [PATCH 0/2] exec: Fix dead-lock in de_thread with ptrace_attach >> [PATCH 1/2] exec: Fix dead-lock in de_thread with ptrace_attach >> [PATCH 2/2] doc: Update documentation of ->exec_*_mutex >> >> >> Other patches needed, still valid: >> >> [PATCH v2 1/5] exec: Only compute current once in flush_old_exec >> https://lore.kernel.org/lkml/87pndm5y3l.fsf_-_@x220.int.ebiederm.org/ >> >> [PATCH v2 2/5] exec: Factor unshare_sighand out of de_thread and call it separately >> https://lore.kernel.org/lkml/87k13u5y26.fsf_-_@x220.int.ebiederm.org/ >> > > Ah, sorry, forgot this one: > [PATCH v2 3/5] exec: Move cleanup of posix timers on exec out of de_thread > https://lore.kernel.org/lkml/87eeu25y14.fsf_-_@x220.int.ebiederm.org/ > >> [PATCH v2 4/5] exec: Move exec_mmap right after de_thread in flush_old_exec >> https://lore.kernel.org/lkml/875zfe5xzb.fsf_-_@x220.int.ebiederm.org/ 1-4/5 look OK for me. You may add my Reviewed-by: Kirill Tkhai >> [PATCH 1/4] exec: Fix a deadlock in ptrace >> https://lore.kernel.org/lkml/AM6PR03MB517033EAD25BED15CC84E17DE4FF0@AM6PR03MB5170.eurprd03.prod.outlook.com/ >> >> [PATCH 2/4] selftests/ptrace: add test cases for dead-locks >> https://lore.kernel.org/lkml/AM6PR03MB51703199741A2C27A78980FFE4FF0@AM6PR03MB5170.eurprd03.prod.outlook.com/ >> >> [PATCH 3/4] mm: docs: Fix a comment in process_vm_rw_core >> https://lore.kernel.org/lkml/AM6PR03MB5170ED6D4D216EEEEF400136E4FF0@AM6PR03MB5170.eurprd03.prod.outlook.com/ >> >> [PATCH 4/4] kernel: doc: remove outdated comment cred.c >> https://lore.kernel.org/lkml/AM6PR03MB517039DB07AB641C194FEA57E4FF0@AM6PR03MB5170.eurprd03.prod.outlook.com/ >> >> [PATCH 1/4] kernel/kcmp.c: Use new infrastructure to fix deadlocks in execve >> https://lore.kernel.org/lkml/AM6PR03MB517057A2269C3A4FB287B76EE4FF0@AM6PR03MB5170.eurprd03.prod.outlook.com/ >> >> [PATCH 2/4] proc: Use new infrastructure to fix deadlocks in execve >> https://lore.kernel.org/lkml/AM6PR03MB51705D211EC8E7EA270627B1E4FF0@AM6PR03MB5170.eurprd03.prod.outlook.com/ >> >> [PATCH 3/4] proc: io_accounting: Use new infrastructure to fix deadlocks in execve >> https://lore.kernel.org/lkml/AM6PR03MB5170BD2476E35068E182EFA4E4FF0@AM6PR03MB5170.eurprd03.prod.outlook.com/ >> >> [PATCH 4/4] perf: Use new infrastructure to fix deadlocks in execve >> https://lore.kernel.org/lkml/AM6PR03MB517035DEEDB9C8699CB6B34EE4FF0@AM6PR03MB5170.eurprd03.prod.outlook.com/ >> >> >> I think most of the existing patches are already approved, but if >> there are still change requests, please let me know. >> >> >> Thanks >> Bernd. >> > > Hope it is correct now. > I haven't seen the new patches on the kernel archives yet, > so I cannot add URLs for them. > > Bernd. >