From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752079Ab2AYXac (ORCPT ); Wed, 25 Jan 2012 18:30:32 -0500 Received: from mail.linuxfoundation.org ([140.211.169.12]:56990 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750772Ab2AYXaa (ORCPT ); Wed, 25 Jan 2012 18:30:30 -0500 Date: Wed, 25 Jan 2012 15:30:28 -0800 From: Andrew Morton To: Kees Cook Cc: linux-kernel@vger.kernel.org, Linus Torvalds , Randy Dunlap , Borislav Petkov , Vasiliy Kulikov , Dan Ballard , Jiri Kosina , Al Viro , Stephen Wilson , David Rientjes , Ingo Molnar , Peter Zijlstra , Eric Paris , "Serge E. Hallyn" , linux-doc@vger.kernel.org, "Eric W. Biederman" , Colin Walters Subject: Re: [PATCH v3] sysctl: control functionality of /proc/pid/mem Message-Id: <20120125153028.17d69f6e.akpm@linux-foundation.org> In-Reply-To: <20120123212115.GA29641@www.outflux.net> References: <20120123212115.GA29641@www.outflux.net> X-Mailer: Sylpheed 3.0.2 (GTK+ 2.20.1; 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 List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, 23 Jan 2012 13:21:15 -0800 Kees Cook wrote: > > Add the "proc_pid_mem" sysctl to control whether or not /proc/pid/mem is > allowed to work: 0: disabled, 1: read only, 2: read/write (default). > > Signed-off-by: Kees Cook > --- > v3: > - document the default, thanks to Randy Dunlap. > - remove needless CONFIG_PROC_FS checks, thanks to Eric W. Biederman. I was wondering about that. Is CONFIG_PROC_FS=n, CONFIG_SYSCTL=y an impossible combination? If so, why? > --- a/Documentation/sysctl/kernel.txt > +++ b/Documentation/sysctl/kernel.txt > @@ -56,6 +56,7 @@ show up in /proc/sys/kernel: > - printk_delay > - printk_ratelimit > - printk_ratelimit_burst > +- proc_pid_mem > - randomize_va_space > - real-root-dev ==> Documentation/initrd.txt > - reboot-cmd [ SPARC only ] > @@ -477,6 +478,20 @@ send before ratelimiting kicks in. > > ============================================================== > > +proc_pid_mem: > + > +This option can be used to select the level of access given to potential > +ptracers when using the per-process "mem" file in /proc/pid/mem. > + > +0 - Disable entirely. > + > +1 - Allow potential ptracers read access to process memory, but not writes. > + > +2 - Allow potential ptracers read and write access to process memory. This > + is the default. > + > +============================================================== I agree with Colin on this (he stole my line!). Overall, the patch looks really hacky and random. I felt the same way as Vasily: it's easy to see how a significant number of similar (and hacky and random) patches could be added, resulting in a regrettable mess. Is there some better designed, more organized way of approaching all of this? Random ideas: - A parallel /procfs-perms filesystem. You write a number into /procfs-perms/stat to affect access to /proc/stat (although why the heck not just run `chmod /proc/stat'?) It's unclear how to handle /proc/pid/. Perhaps literally have a /procfs-perms/pid/ directory. - Make tasks inherit their /proc/pid/* permissions across fork, do a chmod /proc/1/whatever in initscripts. - Other and better things ;) This particular approach makes my toes curl.