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=-5.8 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,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 5220DC433E0 for ; Mon, 18 Jan 2021 19:47:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 158E222C9D for ; Mon, 18 Jan 2021 19:47:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2394145AbhARTrK (ORCPT ); Mon, 18 Jan 2021 14:47:10 -0500 Received: from raptor.unsafe.ru ([5.9.43.93]:56470 "EHLO raptor.unsafe.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2394024AbhARTrD (ORCPT ); Mon, 18 Jan 2021 14:47:03 -0500 Received: from example.org (ip-89-103-122-167.net.upcbroadband.cz [89.103.122.167]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits)) (No client certificate requested) by raptor.unsafe.ru (Postfix) with ESMTPSA id 3C0D820479; Mon, 18 Jan 2021 19:45:56 +0000 (UTC) Date: Mon, 18 Jan 2021 20:45:51 +0100 From: Alexey Gladkov To: Linus Torvalds Cc: LKML , io-uring , Kernel Hardening , Linux Containers , Linux-MM , Andrew Morton , Christian Brauner , "Eric W . Biederman" , Jann Horn , Jens Axboe , Kees Cook , Oleg Nesterov Subject: Re: [RFC PATCH v3 1/8] Use refcount_t for ucounts reference counting Message-ID: <20210118194551.h2hrwof7b3q5vgoi@example.org> References: <116c7669744404364651e3b380db2d82bb23f983.1610722473.git.gladkov.alexey@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.6.1 (raptor.unsafe.ru [5.9.43.93]); Mon, 18 Jan 2021 19:46:07 +0000 (UTC) Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Mon, Jan 18, 2021 at 11:14:48AM -0800, Linus Torvalds wrote: > On Fri, Jan 15, 2021 at 6:59 AM Alexey Gladkov wrote: > > > > @@ -152,10 +153,7 @@ static struct ucounts *get_ucounts(struct user_namespace *ns, kuid_t uid) > > ucounts = new; > > } > > } > > - if (ucounts->count == INT_MAX) > > - ucounts = NULL; > > - else > > - ucounts->count += 1; > > + refcount_inc(&ucounts->count); > > spin_unlock_irq(&ucounts_lock); > > return ucounts; > > } > > This is wrong. > > It used to return NULL when the count saturated. > > Now it just silently saturates. > > I'm not sure how many people care, but that NULL return ends up being > returned quite widely (through "inc_uncount()" and friends). > > The fact that this has no commit message at all to explain what it is > doing and why is also a grounds for just NAK. Sorry about that. I thought that this code is not needed when switching from int to refcount_t. I was wrong. I'll think about how best to check it. -- Rgrds, legion