From patchwork Sun Mar 8 21:34:37 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Eric W. Biederman" X-Patchwork-Id: 11425839 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id E7E671731 for ; Sun, 8 Mar 2020 21:37:03 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CAC0620684 for ; Sun, 8 Mar 2020 21:37:03 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726368AbgCHVhA (ORCPT ); Sun, 8 Mar 2020 17:37:00 -0400 Received: from out02.mta.xmission.com ([166.70.13.232]:45608 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726346AbgCHVg7 (ORCPT ); Sun, 8 Mar 2020 17:36:59 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out02.mta.xmission.com with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jB3bT-0007ZJ-0B; Sun, 08 Mar 2020 15:36:55 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95] helo=x220.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.87) (envelope-from ) id 1jB3bS-00064F-7L; Sun, 08 Mar 2020 15:36:54 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Bernd Edlinger 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: <87k142lpfz.fsf@x220.int.ebiederm.org> <875zfmloir.fsf@x220.int.ebiederm.org> <87v9nmjulm.fsf@x220.int.ebiederm.org> <202003021531.C77EF10@keescook> <20200303085802.eqn6jbhwxtmz4j2x@wittgenstein> <87v9nlii0b.fsf@x220.int.ebiederm.org> <87a74xi4kz.fsf@x220.int.ebiederm.org> <87r1y8dqqz.fsf@x220.int.ebiederm.org> <87tv32cxmf.fsf_-_@x220.int.ebiederm.org> Date: Sun, 08 Mar 2020 16:34:37 -0500 In-Reply-To: <87tv32cxmf.fsf_-_@x220.int.ebiederm.org> (Eric W. Biederman's message of "Thu, 05 Mar 2020 15:14:48 -0600") Message-ID: <87v9ne5y4y.fsf_-_@x220.int.ebiederm.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 X-XM-SPF: eid=1jB3bS-00064F-7L;;;mid=<87v9ne5y4y.fsf_-_@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18D3Lt6XSlAz5TMYYPswZO8/Y7S8x0tW1Y= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on sa07.xmission.com X-Spam-Level: X-Spam-Status: No, score=0.5 required=8.0 tests=ALL_TRUSTED,BAYES_40, DCC_CHECK_NEGATIVE,XMNoVowels autolearn=disabled version=3.4.2 X-Spam-Report: * -1.0 ALL_TRUSTED Passed through trusted hosts only via SMTP * -0.0 BAYES_40 BODY: Bayes spam probability is 20 to 40% * [score: 0.3850] * 1.5 XMNoVowels Alpha-numberic number with no vowels * -0.0 DCC_CHECK_NEGATIVE Not listed in DCC * [sa07 1397; Body=1 Fuz1=1 Fuz2=1] X-Spam-DCC: XMission; sa07 1397; Body=1 Fuz1=1 Fuz2=1 X-Spam-Combo: ;Bernd Edlinger X-Spam-Relay-Country: X-Spam-Timing: total 312 ms - load_scoreonly_sql: 0.04 (0.0%), signal_user_changed: 3.1 (1.0%), b_tie_ro: 2.1 (0.7%), parse: 1.00 (0.3%), extract_message_metadata: 2.7 (0.9%), get_uri_detail_list: 0.93 (0.3%), tests_pri_-1000: 7 (2.3%), tests_pri_-950: 1.16 (0.4%), tests_pri_-900: 1.12 (0.4%), tests_pri_-90: 38 (12.1%), check_bayes: 36 (11.4%), b_tokenize: 18 (5.7%), b_tok_get_all: 9 (2.8%), b_comp_prob: 3.1 (1.0%), b_tok_touch_all: 3.6 (1.2%), b_finish: 0.98 (0.3%), tests_pri_0: 239 (76.5%), check_dkim_signature: 0.81 (0.3%), check_dkim_adsp: 2.4 (0.8%), poll_dns_idle: 0.37 (0.1%), tests_pri_10: 2.1 (0.7%), tests_pri_500: 10 (3.1%), rewrite_mail: 0.00 (0.0%) Subject: [PATCH 0/5] Infrastructure to allow fixing exec deadlocks 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 in02.mta.xmission.com) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Bernd, everyone This is how I think the infrastructure change should look that makes way for fixing this issue. - Cleanup and reorder the code so code that can potentially wait indefinitely for userspace comes at the beginning for flush_old_exec. - Add a new mutex and take it after we have passed any potential indefinite waits for userspace. Then I think it is just going through the existing users of cred_guard_mutex and fixing them to use the new one. There really aren't that many users of cred_guard_mutex so we should be able to get through the easy ones fairly quickly. And anything that isn't easy we can wait until we have a good fix. The users of cred_guard_mutex that I saw were: fs/proc/base.c: proc_pid_attr_write do_io_accounting proc_pid_stack proc_pid_syscall proc_pid_personality perf_event_open mm_access kcmp pidfd_fget seccomp_set_mode_filter Bernd I think I have addressed the issues you pointed out in v1. Please let me know if you see anything else. Eric W. Biederman (5): exec: Only compute current once in flush_old_exec exec: Factor unshare_sighand out of de_thread and call it separately exec: Move cleanup of posix timers on exec out of de_thread exec: Move exec_mmap right after de_thread in flush_old_exec exec: Add a exec_update_mutex to replace cred_guard_mutex fs/exec.c | 65 ++++++++++++++++++++++++++++++-------------- include/linux/sched/signal.h | 9 +++++- init/init_task.c | 1 + kernel/fork.c | 1 + 4 files changed, 54 insertions(+), 22 deletions(-)