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 56B9BC2D0DB for ; Wed, 22 Jan 2020 14:27:55 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 111E9217F4 for ; Wed, 22 Jan 2020 14:27:54 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 111E9217F4 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Received: from lists.ozlabs.org (lists.ozlabs.org [IPv6:2401:3900:2:1::3]) by lists.ozlabs.org (Postfix) with ESMTP id 482nn3388gzDqV4 for ; Thu, 23 Jan 2020 01:27:51 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.helo=mga12.intel.com (client-ip=192.55.52.136; helo=mga12.intel.com; envelope-from=alexey.budankov@linux.intel.com; receiver=) Authentication-Results: lists.ozlabs.org; dmarc=none (p=none dis=none) header.from=linux.intel.com Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 482nkJ2WvZzDqRs for ; Thu, 23 Jan 2020 01:25:25 +1100 (AEDT) X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga002.fm.intel.com ([10.253.24.26]) by fmsmga106.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 22 Jan 2020 06:25:21 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,350,1574150400"; d="scan'208";a="259481099" Received: from linux.intel.com ([10.54.29.200]) by fmsmga002.fm.intel.com with ESMTP; 22 Jan 2020 06:25:20 -0800 Received: from [10.252.5.6] (unknown [10.252.5.6]) by linux.intel.com (Postfix) with ESMTP id C8A54580100; Wed, 22 Jan 2020 06:25:10 -0800 (PST) Subject: Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel and user space To: Stephen Smalley , Alexei Starovoitov 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> <537bdb28-c9e4-f44f-d665-25250065a6bb@linux.intel.com> <63d9700f-231d-7973-5307-3e56a48c54cb@linux.intel.com> From: Alexey Budankov Organization: Intel Corp. Message-ID: Date: Wed, 22 Jan 2020 17:25:09 +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: 8bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , Song Liu , Peter Zijlstra , "joonas.lahtinen@linux.intel.com" , Will Deacon , Alexei Starovoitov , Stephane Eranian , "james.bottomley@hansenpartnership.com" , Paul Mackerras , Jiri Olsa , Andi Kleen , Igor Lubashev , James Morris , Alexander Shishkin , Ingo Molnar , oprofile-list@lists.sf.net, Serge Hallyn , Robert Richter , "selinux@vger.kernel.org" , "intel-gfx@lists.freedesktop.org" , "jani.nikula@linux.intel.com" , Arnaldo Carvalho de Melo , "rodrigo.vivi@intel.com" , Namhyung Kim , Thomas Gleixner , linux-arm-kernel , "linux-parisc@vger.kernel.org" , linux-kernel , Lionel Landwerlin , Andy Lutomirski , "linux-perf-users@vger.kernel.org" , "linux-security-module@vger.kernel.org" , "linuxppc-dev@lists.ozlabs.org" Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 22.01.2020 17:07, Stephen Smalley wrote: > On 1/22/20 5:45 AM, Alexey Budankov wrote: >> >> On 21.01.2020 21:27, Alexey Budankov wrote: >>> >>> 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. >> >> So far so good, I suggest using the simplest version for v6: >> >> static inline bool perfmon_capable(void) >> { >> return capable(CAP_PERFMON) || capable(CAP_SYS_ADMIN); >> } >> >> It keeps the implementation simple and readable. The implementation is more >> performant in the sense of calling the API - one capable() call for CAP_PERFMON >> privileged process. >> >> Yes, it bloats audit log for CAP_SYS_ADMIN privileged and unprivileged processes, >> but this bloating also advertises and leverages using more secure CAP_PERFMON >> based approach to use perf_event_open system call. > > I can live with that. We just need to document that when you see both a CAP_PERFMON and a CAP_SYS_ADMIN audit message for a process, try only allowing CAP_PERFMON first and see if that resolves the issue. We have a similar issue with CAP_DAC_READ_SEARCH versus CAP_DAC_OVERRIDE. perf security [1] document can be updated, at least, to align and document this audit logging specifics. ~Alexey [1] https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html