Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S938873AbcJRUtA (ORCPT ); Tue, 18 Oct 2016 16:49:00 -0400 Received: from mail-wm0-f49.google.com ([74.125.82.49]:36844 "EHLO mail-wm0-f49.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S935636AbcJRUsd (ORCPT ); Tue, 18 Oct 2016 16:48:33 -0400 MIME-Version: 1.0 In-Reply-To: <20161017134413.GK29095@leverpostej> References: <1469630746-32279-1-git-send-email-jeffv@google.com> <20161017134413.GK29095@leverpostej> From: Kees Cook Date: Tue, 18 Oct 2016 13:48:30 -0700 X-Google-Sender-Auth: NNspFMqbFNxqBBNLKptfiEl4uHA Message-ID: Subject: Re: [kernel-hardening] [PATCH 1/2] security, perf: allow further restriction of perf_event_open To: Mark Rutland Cc: "kernel-hardening@lists.openwall.com" , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , "linux-doc@vger.kernel.org" , LKML , Jeff Vander Stoep Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1801 Lines: 42 On Mon, Oct 17, 2016 at 6:44 AM, Mark Rutland wrote: > Hi, > > Attempt to revive discussions below... > > On Wed, Jul 27, 2016 at 07:45:46AM -0700, Jeff Vander Stoep wrote: >> When kernel.perf_event_paranoid is set to 3 (or greater), disallow >> all access to performance events by users without CAP_SYS_ADMIN. >> >> This new level of restriction is intended to reduce the attack >> surface of the kernel. Perf is a valuable tool for developers but >> is generally unnecessary and unused on production systems. Perf may >> open up an attack vector to vulnerable device-specific drivers as >> recently demonstrated in CVE-2016-0805, CVE-2016-0819, >> CVE-2016-0843, CVE-2016-3768, and CVE-2016-3843. This new level of >> restriction allows for a safe default to be set on production systems >> while leaving a simple means for developers to grant access [1]. >> >> This feature is derived from CONFIG_GRKERNSEC_PERF_HARDEN by Brad >> Spengler. It is based on a patch by Ben Hutchings [2]. Ben's patches >> have been modified and split up to address on-list feedback. >> >> kernel.perf_event_paranoid=3 is the default on both Debian [2] and >> Android [3]. > > While people weren't particularly happy with this global toggle > approach, my understanding from face-to-face discussions at LSS2016 was > that people were happy with a more scoped restriction (e.g. using > capabilities or some other access control mechanism), but no-one had the > time to work on that. > > Does that match everyone's understanding, or am I mistaken? That's correct: some kind of finer-grain control would be preferred to the maintainer, but no one has had time to work on it. (The =3 sysctl setting present in Android, Debian, and Ubuntu satisfies most people.) -Kees -- Kees Cook Nexus Security