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=ham 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 43D2DC2D0CE for ; Tue, 21 Jan 2020 18:27:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 1CE7724656 for ; Tue, 21 Jan 2020 18:27:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729235AbgAUS1x (ORCPT ); Tue, 21 Jan 2020 13:27:53 -0500 Received: from mga18.intel.com ([134.134.136.126]:29552 "EHLO mga18.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728186AbgAUS1x (ORCPT ); Tue, 21 Jan 2020 13:27:53 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga006.jf.intel.com ([10.7.209.51]) by orsmga106.jf.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 21 Jan 2020 10:27:52 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,346,1574150400"; d="scan'208";a="228946136" Received: from linux.intel.com ([10.54.29.200]) by orsmga006.jf.intel.com with ESMTP; 21 Jan 2020 10:27:52 -0800 Received: from [10.252.13.111] (abudanko-mobl.ccr.corp.intel.com [10.252.13.111]) by linux.intel.com (Postfix) with ESMTP id 76FDE58033E; Tue, 21 Jan 2020 10:27:42 -0800 (PST) Subject: Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space To: Alexei Starovoitov , Stephen Smalley Cc: 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 , 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 , "linux-perf-users@vger.kernel.org" , oprofile-list@lists.sf.net, Andy Lutomirski 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> <05297eff-8e14-ccdf-55a4-870c64516de8@linux.intel.com> From: Alexey Budankov Organization: Intel Corp. Message-ID: <537bdb28-c9e4-f44f-d665-25250065a6bb@linux.intel.com> Date: Tue, 21 Jan 2020 21:27:41 +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: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: On 21.01.2020 20:55, Alexei Starovoitov wrote: > On Tue, Jan 21, 2020 at 9:31 AM Alexey Budankov > wrote: >> >> >> 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, in the requested changes form v4 I wrote: > return capable(CAP_PERFMON); > instead of > return false; Aww, indeed. I was concerning exactly about it when updating the patch and simply put false, missing the fact that capable() also logs. I suppose the idea is originally from here [1]. BTW, Has it already seen any _more optimal_ implementation? Anyway, original or optimized version could be reused for CAP_PERFMON. ~Alexey [1] https://patchwork.ozlabs.org/patch/1159243/ > > That's what Andy suggested earlier for CAP_BPF. > I think that should resolve Stephen's concern. >