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=-5.3 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham 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 0F954C433E0 for ; Wed, 20 May 2020 01:14:23 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id E1A9320708 for ; Wed, 20 May 2020 01:14:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728188AbgETBOW (ORCPT ); Tue, 19 May 2020 21:14:22 -0400 Received: from szxga06-in.huawei.com ([45.249.212.32]:56808 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726178AbgETBOV (ORCPT ); Tue, 19 May 2020 21:14:21 -0400 Received: from DGGEMS404-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 45F0110543B7D5B6A0A6; Wed, 20 May 2020 09:14:19 +0800 (CST) Received: from [127.0.0.1] (10.67.102.197) by DGGEMS404-HUB.china.huawei.com (10.3.19.204) with Microsoft SMTP Server id 14.3.487.0; Wed, 20 May 2020 09:14:08 +0800 Subject: Re: [PATCH v4 2/4] sysctl: Move some boundary constants form sysctl.c to sysctl_vals To: Tetsuo Handa , CC: , , , , , , , , , , , , , , , , , , , , References: <1589859071-25898-1-git-send-email-nixiaoming@huawei.com> <1589859071-25898-3-git-send-email-nixiaoming@huawei.com> <1bf1aefb-adfd-4f43-35c7-5b320d43faf8@i-love.sakura.ne.jp> From: Xiaoming Ni Message-ID: <550a55b8-d2a8-0de3-0bed-8f93a4513efe@huawei.com> Date: Wed, 20 May 2020 09:14:08 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: <1bf1aefb-adfd-4f43-35c7-5b320d43faf8@i-love.sakura.ne.jp> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.67.102.197] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/5/19 12:44, Tetsuo Handa wrote: > On 2020/05/19 12:31, Xiaoming Ni wrote: >> Some boundary (.extra1 .extra2) constants (E.g: neg_one two) in >> sysctl.c are used in multiple features. Move these variables to >> sysctl_vals to avoid adding duplicate variables when cleaning up >> sysctls table. >> >> Signed-off-by: Xiaoming Ni >> Reviewed-by: Kees Cook > > I feel that it is use of > > void *extra1; > void *extra2; > > in "struct ctl_table" that requires constant values indirection. > Can't we get rid of sysctl_vals using some "union" like below? > > struct ctl_table { > const char *procname; /* Text ID for /proc/sys, or zero */ > void *data; > int maxlen; > umode_t mode; > struct ctl_table *child; /* Deprecated */ > proc_handler *proc_handler; /* Callback for text formatting */ > struct ctl_table_poll *poll; > union { > void *min_max_ptr[2]; > int min_max_int[2]; > long min_max_long[2]; > }; > } __randomize_layout; > > . > net/decnet/dn_dev.c: static void dn_dev_sysctl_register(struct net_device *dev, struct dn_dev_parms *parms) { struct dn_dev_sysctl_table *t; int i; char path[sizeof("net/decnet/conf/") + IFNAMSIZ]; t = kmemdup(&dn_dev_sysctl, sizeof(*t), GFP_KERNEL); if (t == NULL) return; for(i = 0; i < ARRAY_SIZE(t->dn_dev_vars) - 1; i++) { long offset = (long)t->dn_dev_vars[i].data; t->dn_dev_vars[i].data = ((char *)parms) + offset; } snprintf(path, sizeof(path), "net/decnet/conf/%s", dev? dev->name : parms->name); t->dn_dev_vars[0].extra1 = (void *)dev; t->sysctl_header = register_net_sysctl(&init_net, path, t->dn_dev_vars); if (t->sysctl_header == NULL) kfree(t); else parms->sysctl = t; } A small amount of code is not used as a boundary value when using extra1. This scenario may not be suitable for renaming to min_max_ptr. Should we add const to extra1 extra2 ? --- a/include/linux/sysctl.h +++ b/include/linux/sysctl.h @@ -124,8 +124,8 @@ struct ctl_table { struct ctl_table *child; /* Deprecated */ proc_handler *proc_handler; /* Callback for text formatting */ struct ctl_table_poll *poll; - void *extra1; - void *extra2; + const void *extra1; + const void *extra2; } __randomize_layout; Thanks Xiaoming Ni