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=-0.8 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,URIBL_BLOCKED autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by aws-us-west-2-korg-lkml-1.web.codeaurora.org (Postfix) with ESMTP id 2C9B3C5CFF1 for ; Tue, 12 Jun 2018 23:36:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id E049520891 for ; Tue, 12 Jun 2018 23:36:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E049520891 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=linux-foundation.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934898AbeFLXgJ (ORCPT ); Tue, 12 Jun 2018 19:36:09 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36994 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934156AbeFLXgD (ORCPT ); Tue, 12 Jun 2018 19:36:03 -0400 Received: from akpm3.svl.corp.google.com (unknown [104.133.9.92]) by mail.linuxfoundation.org (Postfix) with ESMTPSA id EA859FDC; Tue, 12 Jun 2018 23:36:02 +0000 (UTC) Date: Tue, 12 Jun 2018 16:36:01 -0700 From: Andrew Morton To: Takashi Iwai Cc: Davidlohr Bueso , linux-kernel@vger.kernel.org, Waiman Long Subject: Re: [PATCH] ipc: Limit sysctl value to IPCMNI Message-Id: <20180612163601.bef7f58dadda2832b36db3f6@linux-foundation.org> In-Reply-To: References: <20180608134949.12672-1-tiwai@suse.de> <20180608141659.8a517b128c756b4d0b813c9e@linux-foundation.org> <20180611161845.6164d3a6c2df353fe11895bf@linux-foundation.org> X-Mailer: Sylpheed 3.6.0 (GTK+ 2.24.31; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 12 Jun 2018 08:36:32 +0200 Takashi Iwai wrote: > > Well the present behaviour is to convert higher values downwards, yes? > > > > int ipc_addid(struct ipc_ids *ids, struct kern_ipc_perm *new, int limit) > > { > > kuid_t euid; > > kgid_t egid; > > int id, err; > > > > if (limit > IPCMNI) > > limit = IPCMNI; > > > > So if someone out there is presently setting this to 999999 then their > > kernel will work just fine. After your proposed change, it will no > > longer do so - the tuning attempt will fail with -EINVAL. > > > > It really does us no good to say "you shouldn't have been doing that". > > The fact that they *are* doing it and that it works OK is the kernel > > developers' fault for not applying suitable checking on day one. I > > think we're stuck with continuing to accept such input. > > Hm, that's one concern, yes. > > OTOH, we do secretly ignore the input value, and this isn't what's > expected by user, either. Moreover, user-space has no slightest idea > which value can be accepted and which not. > > Actually I posted it just because of requests from customers who > needed to raise the bar, but didn't notice the effect. > > Maybe another possible solution would be to add another proc entry to > handle this correctly, and make the old one only for compatibility. Yes, I guess so. Just leave the old tunable alone. Possibly we could add a printk_once("please switch to the new interface").