From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-6.0 required=5.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham autolearn_force=no version=3.4.2 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 7701C7D04D for ; Thu, 7 Feb 2019 13:31:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727057AbfBGNbe (ORCPT ); Thu, 7 Feb 2019 08:31:34 -0500 Received: from mga05.intel.com ([192.55.52.43]:39123 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726983AbfBGNbd (ORCPT ); Thu, 7 Feb 2019 08:31:33 -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 fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 07 Feb 2019 05:31:33 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.58,344,1544515200"; d="scan'208";a="114406966" Received: from linux.intel.com ([10.54.29.200]) by orsmga006.jf.intel.com with ESMTP; 07 Feb 2019 05:31:32 -0800 Received: from [10.125.252.152] (abudanko-mobl.ccr.corp.intel.com [10.125.252.152]) by linux.intel.com (Postfix) with ESMTP id E81C55800E0; Thu, 7 Feb 2019 05:31:28 -0800 (PST) Subject: [PATCH v2 3/4] perf-security: elaborate on perf_events/Perf privileged users From: Alexey Budankov To: Jonatan Corbet , Kees Cook , Thomas Gleixner , Ingo Molnar , Peter Zijlstra Cc: Jann Horn , Arnaldo Carvalho de Melo , Jiri Olsa , Namhyung Kim , Alexander Shishkin , Andi Kleen , Mark Rutland , Tvrtko Ursulin , "kernel-hardening@lists.openwall.com" , "linux-doc@vger.kernel.org" , linux-kernel References: Organization: Intel Corp. Message-ID: Date: Thu, 7 Feb 2019 16:31:27 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org Elaborate on possible perf_event/Perf privileged users groups and document steps about creating such groups. Signed-off-by: Alexey Budankov --- Changes in v2: - applied comments on v1 --- Documentation/admin-guide/perf-security.rst | 43 +++++++++++++++++++++ 1 file changed, 43 insertions(+) diff --git a/Documentation/admin-guide/perf-security.rst b/Documentation/admin-guide/perf-security.rst index e6eb7e1ee5ad..f27a62805651 100644 --- a/Documentation/admin-guide/perf-security.rst +++ b/Documentation/admin-guide/perf-security.rst @@ -73,6 +73,48 @@ enable capturing of additional data required for later performance analysis of monitored processes or a system. For example, CAP_SYSLOG capability permits reading kernel space memory addresses from /proc/kallsyms file. +perf_events/Perf privileged users +--------------------------------- + +Mechanisms of capabilities, privileged capability-dumb files [6]_ and file system +ACLs [10]_ can be used to create a dedicated group of perf_events/Perf privileged +users who are permitted to execute performance monitoring without scope limits. +The following steps can be taken to create such a group of privileged Perf users. + +1. Create perf_users group of privileged Perf users, assign perf_users group to + Perf tool executable and limit access to the executable for other users in the + system who are not in the perf_users group: + +:: + + # groupadd perf_users + # ls -alhF + -rwxr-xr-x 2 root root 11M Oct 19 15:12 perf + # chgrp perf_users perf + # ls -alhF + -rwxr-xr-x 2 root perf_users 11M Oct 19 15:12 perf + # chmod o-rwx perf + # ls -alhF + -rwxr-x--- 2 root perf_users 11M Oct 19 15:12 perf + +2. Assign the required capabilities to the Perf tool executable file and enable + members of perf_users group with performance monitoring privileges [6]_ : + +:: + + # setcap "cap_sys_admin,cap_sys_ptrace,cap_syslog=ep" perf + # setcap -v "cap_sys_admin,cap_sys_ptrace,cap_syslog=ep" perf + perf: OK + # getcap perf + perf = cap_sys_ptrace,cap_sys_admin,cap_syslog+ep + +As a result, members of perf_users group are capable of conducting performance +monitoring by using functionality of the configured Perf tool executable that, +when executes, passes perf_events subsystem scope checks. + +This specific access control management is only available to superuser or root +running processes with CAP_SETPCAP, CAP_SETFCAP [6]_ capabilities. + perf_events/Perf unprivileged users ----------------------------------- @@ -156,6 +198,7 @@ Bibliography .. [7] ``_ .. [8] ``_ .. [9] ``_ +.. [10] ``_ .. [11] ``_ .. [12] ``_