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=-3.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 84A03C11F68 for ; Tue, 29 Jun 2021 17:09:47 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6D33E61DD2 for ; Tue, 29 Jun 2021 17:09:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232755AbhF2RMN (ORCPT ); Tue, 29 Jun 2021 13:12:13 -0400 Received: from out01.mta.xmission.com ([166.70.13.231]:49060 "EHLO out01.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232658AbhF2RMK (ORCPT ); Tue, 29 Jun 2021 13:12:10 -0400 Received: from in02.mta.xmission.com ([166.70.13.52]) by out01.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1lyHF0-008vqB-Mu; Tue, 29 Jun 2021 11:09:42 -0600 Received: from ip68-227-160-95.om.om.cox.net ([68.227.160.95]:60780 helo=email.xmission.com) by in02.mta.xmission.com with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1lyHEy-0020Vr-Mu; Tue, 29 Jun 2021 11:09:42 -0600 From: ebiederm@xmission.com (Eric W. Biederman) To: Linus Torvalds Cc: Alexey Gladkov , Linux Kernel Mailing List , Linux Containers References: <87fsx1vcr9.fsf@disp2133> <87czs4u0rm.fsf@disp2133> <87mtr8sjvr.fsf@disp2133> Date: Tue, 29 Jun 2021 12:09:01 -0500 In-Reply-To: <87mtr8sjvr.fsf@disp2133> (Eric W. Biederman's message of "Tue, 29 Jun 2021 11:42:00 -0500") Message-ID: <87a6n8simq.fsf@disp2133> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain X-XM-SPF: eid=1lyHEy-0020Vr-Mu;;;mid=<87a6n8simq.fsf@disp2133>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX18eZPW1C7TY8UVdKymDCO/XEtzG8z7YA2M= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [GIT PULL] ucounts: Count rlimits in each user namespace X-SA-Exim-Version: 4.2.1 (built Sat, 08 Feb 2020 21:53:50 +0000) X-SA-Exim-Scanned: Yes (on in02.mta.xmission.com) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org ebiederm@xmission.com (Eric W. Biederman) writes: > Linus Torvalds writes: > >> On Tue, Jun 29, 2021 at 8:52 AM Eric W. Biederman wrote: >>> >>> Linus Torvalds writes: >>> >>> > Why the "sigpending < LONG_MAX" test in that >>> > >>> > if (override_rlimit || (sigpending < LONG_MAX && sigpending <= >>> > task_rlimit(t, RLIMIT_SIGPENDING))) { >>> > thing? >>> >>> On second look that sigpending < LONG_MAX check is necessary. When >>> inc_rlimit_ucounts detects a problem it returns LONG_MAX. >> >> I saw that, but _without_ that test you'd be left with just that >> >> sigpending <= task_rlimit(t, RLIMIT_SIGPENDING) >> >> and if task_rlimit() is LONG_MAX, then that means "no limits", so it is all ok. > > It means no limits locally. The creator of your user namespace might > have had a limit which you are also bound by. > > The other possibility is that inc_rlimits_ucounts caused a sigpending > counter to overflow. In which case we need to fail and run > dec_rlimit_ucounts to keep the counter from staying overflowed. > > So I don't see a clever way to avoid the sigpending < LONG_MAX test. Hmm. I take that back. There is a simple clever way to satisfy all of the tests. - sigpending < LONG_MAX && sigpending <= task_rlimit(t, RLIMIT_SIGPENDING) + sigpending < task_rlimit(t, RLIMIT_SIGPENDING) That would just need a small comment to explain the subtleties. Eric