From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751447AbcFXAXK (ORCPT ); Thu, 23 Jun 2016 20:23:10 -0400 Received: from mail-wm0-f66.google.com ([74.125.82.66]:36254 "EHLO mail-wm0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750799AbcFXAXH (ORCPT ); Thu, 23 Jun 2016 20:23:07 -0400 Subject: Re: [PATCH] capabilities: add capability cgroup controller To: Tejun Heo References: <1466694434-1420-1-git-send-email-toiwoton@gmail.com> <20160623213819.GP3262@mtj.duckdns.org> Cc: linux-kernel@vger.kernel.org, luto@kernel.org, serge@hallyn.com, keescook@chromium.org, Jonathan Corbet , Li Zefan , Johannes Weiner , Serge Hallyn , James Morris , Andrew Morton , David Howells , David Woodhouse , Ard Biesheuvel , "Paul E. McKenney" , Petr Mladek , "open list:DOCUMENTATION" , "open list:CONTROL GROUP (CGROUP)" , "open list:CAPABILITIES" From: Topi Miettinen Openpgp: id=A0F2EB0D8452DA908BEC8E911CF9ADDBD610E936 Message-ID: <53377cda-9afe-dad4-6bbb-26affd64cb3a@gmail.com> Date: Fri, 24 Jun 2016 00:22:54 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Icedove/45.1.0 MIME-Version: 1.0 In-Reply-To: <20160623213819.GP3262@mtj.duckdns.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 06/23/16 21:38, Tejun Heo wrote: > Hello, > > On Thu, Jun 23, 2016 at 06:07:10PM +0300, Topi Miettinen wrote: >> There are many basic ways to control processes, including capabilities, >> cgroups and resource limits. However, there are far fewer ways to find >> out useful values for the limits, except blind trial and error. >> >> Currently, there is no way to know which capabilities are actually used. >> Even the source code is only implicit, in-depth knowledge of each >> capability must be used when analyzing a program to judge which >> capabilities the program will exercise. >> >> Add a new cgroup controller for monitoring of capabilities >> in the cgroup. >> >> Test case demonstrating basic capability monitoring and how the >> capabilities are combined at next level (boot to rdshell): > > This doesn't have anything to do with resource control and I don't > think it's a good idea to add arbitrary monitoring mechanisms to > cgroup just because it's easy to add interface there. Given that > capabilities are inherited and modified through the process hierarchy, > shouldn't this be part of that? With per process tracking, it's easy to miss if a short-lived process exercised capabilities. Especially with ambient capabilities, the parent process could be a shell script which might not use capabilities at all, but its children do the heavy lifting. Per process tracking (like in the version I sent earlier) could still be added on top of this to complement cgroup level tracking, but I think cgroup approach is more flexible as it can cover anything from a single task to a collection of processes. -Topi > > Thanks. >