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=-2.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 BB17BC2D0F0 for ; Mon, 30 Mar 2020 22:09:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9107F206CC for ; Mon, 30 Mar 2020 22:09:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585606184; bh=q2phzh9yFsQx50dV3hbRu31sKC6mnvd0GciRPxzIXns=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=1AnP3hZFHQqBlSQTtS0wL9YDMvpmlqq6JeOKrb4v9gLC/tkdxjm637i20Mn66VF9u 914ORn1ehjBjH+c4wtFRjaZ6qY7A2Yxc6ucBaL8C0RASbuzTWJMZLwYcBwionV7SwW aLyD5Oh77ypxNl9zaroHfcZOfE/6iAroQ+MYgiTM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730808AbgC3WJo (ORCPT ); Mon, 30 Mar 2020 18:09:44 -0400 Received: from mail-pg1-f193.google.com ([209.85.215.193]:40945 "EHLO mail-pg1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729142AbgC3WJn (ORCPT ); Mon, 30 Mar 2020 18:09:43 -0400 Received: by mail-pg1-f193.google.com with SMTP id t24so9342617pgj.7; Mon, 30 Mar 2020 15:09:41 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=j7FmspK21WqfyDNNhuaL3ZlTlaa7O+RnMjIkIEqFuiw=; b=su818cT3WfQlUr0ieQYTl5TpuDrJ7aGCv8uzHlTBm5DZjQy/laMDyPgqzuKvEpMBz8 +ZsQdxJpoCIabRbCtmxtoilJ9VJ0sqHWoQXsLzlV34eSMZaOkGUtMt3as4L+eIUME5up mNBgl4UaB7v0pyVBN8Qxii7+AaVwlFNt0+BHjM8H4txepliJxi7X0Dxrx95zjVDRxYSc aMfo43HCQ6tdMKsi+lChfsXfwqKxicPe/2K4tYaNmyTTpLdrhSy+x7oBnVkIBxWTxGmA QejmHSWUpsH0FSjXxpaZblB/20fIpLqHpXz/4JnxGAtwZXLv0VYz7B/1TxpaSO5UfMrb XeEg== X-Gm-Message-State: ANhLgQ0fdMgRtzQ1Fc2qcoDjKN01AJA8EUncnaHZpnt4Rj5lud2b8Key UA1U5lxEyRn3DQLTunCua8c= X-Google-Smtp-Source: ADFU+vvPzerl8j1+L7xAnyd4gLFIsKX6lP6TPO/c76Xt2g0Nx6dQq/wpEsf4qIQGjiT4CSIoeAaL8g== X-Received: by 2002:a62:1745:: with SMTP id 66mr15223339pfx.291.1585606181235; Mon, 30 Mar 2020 15:09:41 -0700 (PDT) Received: from 42.do-not-panic.com (42.do-not-panic.com. [157.230.128.187]) by smtp.gmail.com with ESMTPSA id b133sm9608378pfb.180.2020.03.30.15.09.39 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 30 Mar 2020 15:09:40 -0700 (PDT) Received: by 42.do-not-panic.com (Postfix, from userid 1000) id 61A9F404B0; Mon, 30 Mar 2020 22:09:39 +0000 (UTC) Date: Mon, 30 Mar 2020 22:09:39 +0000 From: Luis Chamberlain To: "Eric W. Biederman" Cc: Michal Hocko , Vlastimil Babka , Kees Cook , Iurii Zaikin , linux-kernel@vger.kernel.org, linux-api@vger.kernel.org, linux-mm@kvack.org, Ivan Teterevkov , David Rientjes , Matthew Wilcox , "Guilherme G . Piccoli" Subject: Re: [RFC v2 1/2] kernel/sysctl: support setting sysctl parameters from kernel command line Message-ID: <20200330220939.GW11244@42.do-not-panic.com> References: <20200325120345.12946-1-vbabka@suse.cz> <874kuc5b5z.fsf@x220.int.ebiederm.org> <20200326065829.GC27965@dhcp22.suse.cz> <87bloj2skm.fsf@x220.int.ebiederm.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <87bloj2skm.fsf@x220.int.ebiederm.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Thu, Mar 26, 2020 at 07:45:13AM -0500, Eric W. Biederman wrote: > > On Wed 25-03-20 17:20:40, Eric W. Biederman wrote: > plus I want to get very far away from the incorrect idea that you > can have sysctls without compiling in proc support. That is not how > the code works, that is not how the code is tested. Agreed. > It is also worth pointing out that: > > proc_mnt = kern_mount(proc_fs_type); > for_each_sysctl_cmdline() { > ... > file = file_open_root(proc_mnt->mnt_root, proc_mnt, sysctl_path, O_WRONLY, 0); > kernel_write(file, value, value_len); > } > kern_umount(proc_mnt); > > Is not an unreasonable implementation. This: > There are problems with a persistent mount of proc in that it forces > userspace not to use any proc mount options. But a temporary mount of > proc to deal with command line options is not at all unreasonable. > Plus it looks like we can have kern_write do all of the kernel/user > buffer silliness. Is a bit of tribal knowledge worth documenting for the approach taken forward. Vlastimil can you add a little comment mentioning some of this logic? Luis