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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable 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 ADC13C2D0CE for ; Tue, 21 Jan 2020 17:31:13 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 905D921569 for ; Tue, 21 Jan 2020 17:31:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729113AbgAURbK (ORCPT ); Tue, 21 Jan 2020 12:31:10 -0500 Received: from mga05.intel.com ([192.55.52.43]:26746 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728186AbgAURbK (ORCPT ); Tue, 21 Jan 2020 12:31:10 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga008.fm.intel.com ([10.253.24.58]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Jan 2020 09:31:08 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,346,1574150400"; d="scan'208";a="221768046" Received: from linux.intel.com ([10.54.29.200]) by fmsmga008.fm.intel.com with ESMTP; 21 Jan 2020 09:31:04 -0800 Received: from [10.252.13.111] (iganakov-mobl1.ger.corp.intel.com [10.252.13.111]) by linux.intel.com (Postfix) with ESMTP id 874B25803C5; Tue, 21 Jan 2020 09:30:55 -0800 (PST) Subject: Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space To: Stephen Smalley , Peter Zijlstra , Arnaldo Carvalho de Melo , Ingo Molnar , "jani.nikula@linux.intel.com" , "joonas.lahtinen@linux.intel.com" , "rodrigo.vivi@intel.com" , "benh@kernel.crashing.org" , Paul Mackerras , Michael Ellerman , "james.bottomley@hansenpartnership.com" , Serge Hallyn , James Morris , Will Deacon , Mark Rutland , Robert Richter , Alexei Starovoitov Cc: Jiri Olsa , Andi Kleen , Stephane Eranian , Igor Lubashev , Alexander Shishkin , Namhyung Kim , Song Liu , Lionel Landwerlin , Thomas Gleixner , linux-kernel , "linux-security-module@vger.kernel.org" , "selinux@vger.kernel.org" , "intel-gfx@lists.freedesktop.org" , "linux-parisc@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" , linux-arm-kernel@lists.infradead.org, "linux-perf-users@vger.kernel.org" , oprofile-list@lists.sf.net References: <0548c832-7f4b-dc4c-8883-3f2b6d351a08@linux.intel.com> <9b77124b-675d-5ac7-3741-edec575bd425@linux.intel.com> <64cab472-806e-38c4-fb26-0ffbee485367@tycho.nsa.gov> From: Alexey Budankov Organization: Intel Corp. Message-ID: <05297eff-8e14-ccdf-55a4-870c64516de8@linux.intel.com> Date: Tue, 21 Jan 2020 20:30:54 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <64cab472-806e-38c4-fb26-0ffbee485367@tycho.nsa.gov> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On 21.01.2020 17:43, Stephen Smalley wrote: > On 1/20/20 6:23 AM, Alexey Budankov wrote: >> >> Introduce CAP_PERFMON capability designed to secure system performance >> monitoring and observability operations so that CAP_PERFMON would assist >> CAP_SYS_ADMIN capability in its governing role for perf_events, i915_perf >> and other performance monitoring and observability subsystems. >> >> CAP_PERFMON intends to harden system security and integrity during system >> performance monitoring and observability operations by decreasing attack >> surface that is available to a CAP_SYS_ADMIN privileged process [1]. >> Providing access to system performance monitoring and observability >> operations under CAP_PERFMON capability singly, without the rest of >> CAP_SYS_ADMIN credentials, excludes chances to misuse the credentials and >> makes operation more secure. >> >> CAP_PERFMON intends to take over CAP_SYS_ADMIN credentials related to >> system performance monitoring and observability operations and balance >> amount of CAP_SYS_ADMIN credentials following the recommendations in the >> capabilities man page [1] for CAP_SYS_ADMIN: "Note: this capability is >> overloaded; see Notes to kernel developers, below." >> >> Although the software running under CAP_PERFMON can not ensure avoidance >> of related hardware issues, the software can still mitigate these issues >> following the official embargoed hardware issues mitigation procedure [2]. >> The bugs in the software itself could be fixed following the standard >> kernel development process [3] to maintain and harden security of system >> performance monitoring and observability operations. >> >> [1] http://man7.org/linux/man-pages/man7/capabilities.7.html >> [2] https://www.kernel.org/doc/html/latest/process/embargoed-hardware-issues.html >> [3] https://www.kernel.org/doc/html/latest/admin-guide/security-bugs.html >> >> Signed-off-by: Alexey Budankov >> --- >>   include/linux/capability.h          | 12 ++++++++++++ >>   include/uapi/linux/capability.h     |  8 +++++++- >>   security/selinux/include/classmap.h |  4 ++-- >>   3 files changed, 21 insertions(+), 3 deletions(-) >> >> diff --git a/include/linux/capability.h b/include/linux/capability.h >> index ecce0f43c73a..8784969d91e1 100644 >> --- a/include/linux/capability.h >> +++ b/include/linux/capability.h >> @@ -251,6 +251,18 @@ extern bool privileged_wrt_inode_uidgid(struct user_namespace *ns, const struct >>   extern bool capable_wrt_inode_uidgid(const struct inode *inode, int cap); >>   extern bool file_ns_capable(const struct file *file, struct user_namespace *ns, int cap); >>   extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns); >> +static inline bool perfmon_capable(void) >> +{ >> +    struct user_namespace *ns = &init_user_ns; >> + >> +    if (ns_capable_noaudit(ns, CAP_PERFMON)) >> +        return ns_capable(ns, CAP_PERFMON); >> + >> +    if (ns_capable_noaudit(ns, CAP_SYS_ADMIN)) >> +        return ns_capable(ns, CAP_SYS_ADMIN); >> + >> +    return false; >> +} > > Why _noaudit()?  Normally only used when a permission failure is non-fatal to the operation.  Otherwise, we want the audit message. Some of ideas from v4 review. Well, on the second sight, it defenitly should be logged for CAP_SYS_ADMIN. Probably it is not so fatal for CAP_PERFMON, but personally I would unconditionally log it for CAP_PERFMON as well. Good catch, thank you. ~Alexey