Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S965166Ab2JCSjj (ORCPT ); Wed, 3 Oct 2012 14:39:39 -0400 Received: from mail-ie0-f174.google.com ([209.85.223.174]:60779 "EHLO mail-ie0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755485Ab2JCSj2 (ORCPT ); Wed, 3 Oct 2012 14:39:28 -0400 MIME-Version: 1.0 In-Reply-To: References: <20121002234934.GA9194@www.outflux.net> Date: Wed, 3 Oct 2012 11:39:27 -0700 X-Google-Sender-Auth: ysH3XPoNmVMd0WhiEA6J-2_SEjc Message-ID: Subject: Re: [PATCH] mm: use %pK for /proc/vmallocinfo From: Kees Cook To: David Rientjes Cc: linux-kernel@vger.kernel.org, Andrew Morton , Minchan Kim , Joe Perches , Kautuk Consul , linux-mm@kvack.org, Brad Spengler Content-Type: text/plain; charset=ISO-8859-1 X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1487 Lines: 36 On Wed, Oct 3, 2012 at 11:02 AM, David Rientjes wrote: > On Wed, 3 Oct 2012, Kees Cook wrote: > >> > So root does echo 0 > /proc/sys/kernel/kptr_restrict first. Again: what >> > are you trying to protect? >> >> Only CAP_SYS_ADMIN can change the setting. This is, for example, for >> containers, or other situations where a uid 0 process lacking >> CAP_SYS_ADMIN cannot see virtual addresses. It's a very paranoid case, >> yes, but it's part of how this feature was designed. Think of it as >> supporting the recent uid 0 vs ring 0 boundary. :) >> > > The intention of /proc/vmallocinfo being S_IRUSR is obviously to only > allow root to read this information to begin with, so if root lacks > CAP_SYS_ADMIN then it seems the best fix would be to return an empty file > on read()? Or give permission to everybody to read it but only return a > positive count when they have CAP_SYS_ADMIN? > > There's no need to make this so convoluted that you need to have the right > combination of uid, kptr_restrict, CAP_SYS_ADMIN, and CAP_SYSLOG to get > anything valuable out of this file, though. Well, the existing mechanism is using %pK. I see no reason to add additional complexity. -Kees -- Kees Cook Chrome OS Security -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/