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=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 82368C65BAE for ; Mon, 3 Dec 2018 09:42:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 549D521486 for ; Mon, 3 Dec 2018 09:42:17 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 549D521486 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726058AbeLCJmc (ORCPT ); Mon, 3 Dec 2018 04:42:32 -0500 Received: from mga14.intel.com ([192.55.52.115]:28827 "EHLO mga14.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725928AbeLCJmc (ORCPT ); Mon, 3 Dec 2018 04:42:32 -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 fmsmga103.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 03 Dec 2018 01:42:15 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.56,310,1539673200"; d="scan'208";a="106547353" Received: from linux.intel.com ([10.54.29.200]) by fmsmga008.fm.intel.com with ESMTP; 03 Dec 2018 01:42:14 -0800 Received: from [10.125.252.149] (abudanko-mobl.ccr.corp.intel.com [10.125.252.149]) by linux.intel.com (Postfix) with ESMTP id 4AB6B580117; Mon, 3 Dec 2018 01:42:11 -0800 (PST) Subject: Re: [PATCH v4 1/2] Documentation/admin-guide: introduce perf-security.rst file From: Alexey Budankov To: Jonathan Corbet , Peter Zijlstra Cc: Thomas Gleixner , Kees Cook , Jann Horn , Ingo Molnar , Andi Kleen , Alexander Shishkin , Jiri Olsa , Arnaldo Carvalho de Melo , Mark Rutland , Tvrtko Ursulin , linux-kernel , "kernel-hardening@lists.openwall.com" , "linux-doc@vger.kernel.org" References: <20181127111148.75746f02@lwn.net> <5e1e9c08-dff5-956d-4c2b-8ee090c387c3@linux.intel.com> Organization: Intel Corp. Message-ID: Date: Mon, 3 Dec 2018 12:42:09 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <5e1e9c08-dff5-956d-4c2b-8ee090c387c3@linux.intel.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Peter, On 27.11.2018 22:13, Alexey Budankov wrote: > On 27.11.2018 21:11, Jonathan Corbet wrote: >> On Tue, 27 Nov 2018 11:15:37 +0300 >> Alexey Budankov wrote: >> >>> +To perform security checks, the Linux implementation splits processes into two >>> +categories [6]_ : a) privileged processes (whose effective user ID is 0, referred >>> +to as superuser or root), and b) unprivileged processes (whose effective UID is >>> +nonzero). Privileged processes bypass all kernel security permission checks so >>> +perf_events performance monitoring is fully available to privileged processes >>> +without access, scope and resource restrictions. >>> + >>> +Unprivileged processes are subject to a full security permission check based on >>> +the process's credentials [5]_ (usually: effective UID, effective GID, and >>> +supplementary group list). >>> + >>> +Linux divides the privileges traditionally associated with superuser into >>> +distinct units, known as capabilities [6]_ , which can be independently enabled >>> +and disabled on per-thread basis for processes and files of unprivileged users. >>> + >>> +Unprivileged processes with enabled CAP_SYS_ADMIN capability are treated as >>> +privileged processes with respect to perf_events performance monitoring and >>> +bypass *scope* permissions checks in the kernel. >>> + >>> +Unprivileged processes using perf_events system call API is also subject for >>> +PTRACE_MODE_READ_REALCREDS ptrace access mode check [7]_ , whose outcome >>> +determines whether monitoring is permitted. So unprivileged processes provided >>> +with CAP_SYS_PTRACE capability are effectively permitted to pass the check. >> >> It's good to have more information here. I could certainly quibble >> further with things - a process with CAP_SYS_ADMIN is not "unprivileged"! >> - but I don't want to stand in the way of this any further. I *would* >> still like to see an ack from the perf world, though. > > Thanks for meaningful comments! Looking forward to ack from perf world. May I ask you to review v4 of the patches? Your comments on v1 have been addressed in there. Thanks, Alexey > >> >> With regard to Kees's comment on merging the two patches; I would probably >> add the new document to index.rst in the same patch, but it doesn't matter >> that much. Not worth redoing the patch just for that. > > Thanks, > Alexey > >> >> jon >> >