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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F034BC433F5 for ; Mon, 14 Mar 2022 02:49:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235961AbiCNCuU (ORCPT ); Sun, 13 Mar 2022 22:50:20 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50468 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229645AbiCNCuR (ORCPT ); Sun, 13 Mar 2022 22:50:17 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2C18D35DE7 for ; Sun, 13 Mar 2022 19:49:07 -0700 (PDT) Received: from canpemm500002.china.huawei.com (unknown [172.30.72.56]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4KH18B2pRgz1GCMN; Mon, 14 Mar 2022 10:44:10 +0800 (CST) Received: from [10.174.177.76] (10.174.177.76) by canpemm500002.china.huawei.com (7.192.104.244) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2308.21; Mon, 14 Mar 2022 10:49:05 +0800 Subject: Re: [PATCH] mm/mlock: fix potential imbalanced rlimit ucounts adjustment To: Hugh Dickins CC: , , , , References: <20220310132417.41189-1-linmiaohe@huawei.com> <268b3146-2963-15b6-6d6-95a96853314@google.com> From: Miaohe Lin Message-ID: Date: Mon, 14 Mar 2022 10:49:04 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.6.0 MIME-Version: 1.0 In-Reply-To: <268b3146-2963-15b6-6d6-95a96853314@google.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.177.76] X-ClientProxiedBy: dggems702-chm.china.huawei.com (10.3.19.179) To canpemm500002.china.huawei.com (7.192.104.244) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/3/14 10:40, Hugh Dickins wrote: > On Thu, 10 Mar 2022, Miaohe Lin wrote: > >> user_shm_lock forgets to set allowed to 0 when get_ucounts fails. So >> the later user_shm_unlock might do the extra dec_rlimit_ucounts. Fix >> this by resetting allowed to 0. >> >> Fixes: 5ed44a401ddf ("do not limit locked memory when RLIMIT_MEMLOCK is RLIM_INFINITY") >> Signed-off-by: Miaohe Lin > > NAK. user_shm_lock() remembers to declare "int allowed = 0" on entry. > If lock_limit is RLIM_INFINITY, "allowed" will be set to 1. And if get_ucounts fails in some corner cases, "allowed" will remain to be 1 while the user_shm_lock ops indeed fails. Or am I miss something? Many thanks for comment. >> --- >> mm/mlock.c | 1 + >> 1 file changed, 1 insertion(+) >> >> diff --git a/mm/mlock.c b/mm/mlock.c >> index 29372c0eebe5..efd2dd2943de 100644 >> --- a/mm/mlock.c >> +++ b/mm/mlock.c >> @@ -733,6 +733,7 @@ int user_shm_lock(size_t size, struct ucounts *ucounts) >> } >> if (!get_ucounts(ucounts)) { >> dec_rlimit_ucounts(ucounts, UCOUNT_RLIMIT_MEMLOCK, locked); >> + allowed = 0; >> goto out; >> } >> allowed = 1; >> -- >> 2.23.0 >> >> >> > . >