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=-13.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 646A5C433E0 for ; Wed, 13 Jan 2021 16:33:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 10E0C235FA for ; Wed, 13 Jan 2021 16:33:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726880AbhAMQd1 (ORCPT ); Wed, 13 Jan 2021 11:33:27 -0500 Received: from out02.mta.xmission.com ([166.70.13.232]:41676 "EHLO out02.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725747AbhAMQd0 (ORCPT ); Wed, 13 Jan 2021 11:33:26 -0500 Received: from in02.mta.xmission.com ([166.70.13.52]) by out02.mta.xmission.com with esmtps (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1kzj4e-006oSo-Ji; Wed, 13 Jan 2021 09:32:44 -0700 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 (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.93) (envelope-from ) id 1kzj4d-009Vz0-HQ; Wed, 13 Jan 2021 09:32:44 -0700 From: ebiederm@xmission.com (Eric W. Biederman) To: Alexey Gladkov Cc: LKML , Linux Containers , Kernel Hardening , Alexey Gladkov , Kees Cook , Christian Brauner , Linus Torvalds References: <447547b12bba1894d3f1f79d6408dfc60b219b0c.1610299857.git.gladkov.alexey@gmail.com> Date: Wed, 13 Jan 2021 10:31:40 -0600 In-Reply-To: <447547b12bba1894d3f1f79d6408dfc60b219b0c.1610299857.git.gladkov.alexey@gmail.com> (Alexey Gladkov's message of "Sun, 10 Jan 2021 18:33:40 +0100") Message-ID: <878s8wdcib.fsf@x220.int.ebiederm.org> 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=1kzj4d-009Vz0-HQ;;;mid=<878s8wdcib.fsf@x220.int.ebiederm.org>;;;hst=in02.mta.xmission.com;;;ip=68.227.160.95;;;frm=ebiederm@xmission.com;;;spf=neutral X-XM-AID: U2FsdGVkX195fKSBqSZ+lYzEZIXlkNCqt38tQhw2MoY= X-SA-Exim-Connect-IP: 68.227.160.95 X-SA-Exim-Mail-From: ebiederm@xmission.com Subject: Re: [RFC PATCH v2 1/8] Use atomic type for ucounts reference counting 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 Alexey Gladkov writes: We might want to use refcount_t instead of atomic_t. Not a big deal either way. > Signed-off-by: Alexey Gladkov > --- > include/linux/user_namespace.h | 2 +- > kernel/ucount.c | 10 +++++----- > 2 files changed, 6 insertions(+), 6 deletions(-) > > diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h > index 64cf8ebdc4ec..84fefa9247c4 100644 > --- a/include/linux/user_namespace.h > +++ b/include/linux/user_namespace.h > @@ -92,7 +92,7 @@ struct ucounts { > struct hlist_node node; > struct user_namespace *ns; > kuid_t uid; > - int count; > + atomic_t count; > atomic_t ucount[UCOUNT_COUNTS]; > }; > > diff --git a/kernel/ucount.c b/kernel/ucount.c > index 11b1596e2542..0f2c7c11df19 100644 > --- a/kernel/ucount.c > +++ b/kernel/ucount.c > @@ -141,7 +141,8 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) > > new->ns = ns; > new->uid = uid; > - new->count = 0; > + > + atomic_set(&new->count, 0); > > spin_lock_irq(&ucounts_lock); > ucounts = find_ucounts(ns, uid, hashent); > @@ -152,10 +153,10 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) > ucounts = new; > } > } > - if (ucounts->count == INT_MAX) > + if (atomic_read(&ucounts->count) == INT_MAX) > ucounts = NULL; > else > - ucounts->count += 1; > + atomic_inc(&ucounts->count); > spin_unlock_irq(&ucounts_lock); > return ucounts; > } > @@ -165,8 +166,7 @@ static void put_ucounts(struct ucounts *ucounts) > unsigned long flags; > > spin_lock_irqsave(&ucounts_lock, flags); > - ucounts->count -= 1; > - if (!ucounts->count) > + if (atomic_dec_and_test(&ucounts->count)) > hlist_del_init(&ucounts->node); > else > ucounts = NULL; This can become: static void put_ucounts(struct ucounts *ucounts) { unsigned long flags; if (atomic_dec_and_lock_irqsave(&ucounts->count, &ucounts_lock, flags)) { hlist_del_init(&ucounts->node); spin_unlock_irqrestore(&ucounts_lock); kfree(ucounts); } }