From patchwork Mon Feb 17 08:02:15 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Budankov X-Patchwork-Id: 11385525 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id AEEE7924 for ; Mon, 17 Feb 2020 08:02:35 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 911932072C for ; Mon, 17 Feb 2020 08:02:35 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727206AbgBQICZ (ORCPT ); Mon, 17 Feb 2020 03:02:25 -0500 Received: from mga11.intel.com ([192.55.52.93]:16991 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726267AbgBQICY (ORCPT ); Mon, 17 Feb 2020 03:02:24 -0500 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from fmsmga004.fm.intel.com ([10.253.24.48]) by fmsmga102.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 17 Feb 2020 00:02:23 -0800 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,451,1574150400"; d="scan'208";a="258189636" Received: from linux.intel.com ([10.54.29.200]) by fmsmga004.fm.intel.com with ESMTP; 17 Feb 2020 00:02:22 -0800 Received: from [10.125.252.180] (abudanko-mobl.ccr.corp.intel.com [10.125.252.180]) by linux.intel.com (Postfix) with ESMTP id 9B7B558060A; Mon, 17 Feb 2020 00:02:16 -0800 (PST) From: Alexey Budankov Subject: [PATCH v7 00/12] Introduce CAP_PERFMON to secure system performance monitoring and observability To: James Morris , Serge Hallyn , Stephen Smalley , Peter Zijlstra , Arnaldo Carvalho de Melo , Ingo Molnar , "joonas.lahtinen@linux.intel.com" , Alexei Starovoitov , Will Deacon , Paul Mackerras , Helge Deller , Thomas Gleixner Cc: Andi Kleen , Stephane Eranian , Igor Lubashev , Jiri Olsa , linux-kernel , "intel-gfx@lists.freedesktop.org" , "linux-security-module@vger.kernel.org" , "selinux@vger.kernel.org" , linux-arm-kernel , "linuxppc-dev@lists.ozlabs.org" , "linux-parisc@vger.kernel.org" , oprofile-list@lists.sf.net, "linux-doc@vger.kernel.org" , linux-man@vger.kernel.org Organization: Intel Corp. Message-ID: Date: Mon, 17 Feb 2020 11:02:15 +0300 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 MIME-Version: 1.0 Content-Language: en-US Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org Currently access to perf_events, i915_perf and other performance monitoring and observability subsystems of the kernel is open only for a privileged process [1] with CAP_SYS_ADMIN capability enabled in the process effective set [2]. This patch set introduces 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 performance monitoring and observability subsystems of the kernel. CAP_PERFMON intends to harden system security and integrity during performance monitoring and observability operations by decreasing attack surface that is available to a CAP_SYS_ADMIN privileged process [2]. Providing the access to 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 the operation more secure. Thus, CAP_PERFMON implements the principal of least privilege for performance monitoring and observability operations (POSIX IEEE 1003.1e: 2.2.2.39 principle of least privilege: A security design principle that states that a process or program be granted only those privileges (e.g., capabilities) necessary to accomplish its legitimate function, and only for the time that such privileges are actually required) CAP_PERFMON intends to meet the demand to secure system performance monitoring and observability operations for adoption in security sensitive, restricted, multiuser production environments (e.g. HPC clusters, cloud and virtual compute environments), where root or CAP_SYS_ADMIN credentials are not available to mass users of a system, and securely unblock accessibility of system performance monitoring and observability operations beyond root and CAP_SYS_ADMIN use cases. 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 [2] for CAP_SYS_ADMIN: "Note: this capability is overloaded; see Notes to kernel developers, below." For backward compatibility reasons access to system performance monitoring and observability subsystems of the kernel remains open for CAP_SYS_ADMIN privileged processes but CAP_SYS_ADMIN capability usage for secure system performance monitoring and observability operations is discouraged with respect to the designed CAP_PERFMON capability. Possible alternative solution to this system security hardening, capabilities balancing task of making performance monitoring and observability operations more secure and accessible could be to use the existing CAP_SYS_PTRACE capability to govern system performance monitoring and observability subsystems. However CAP_SYS_PTRACE capability still provides users with more credentials than are required for secure performance monitoring and observability operations and this excess is avoided by the designed CAP_PERFMON. Although software running under CAP_PERFMON can not ensure avoidance of related hardware issues, the software can still mitigate those issues following the official hardware issues mitigation procedure [3]. The bugs in the software itself can be fixed following the standard kernel development process [4] to maintain and harden security of system performance monitoring and observability operations. Finally, the patch set is shaped in the way that simplifies backtracking procedure of possible induced issues [5] as much as possible. The patch set is for tip perf/core repository: git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip perf/core sha1: fdb64822443ec9fb8c3a74b598a74790ae8d2e22 Acked-by: Serge E. Hallyn --- Changes in v7: - updated and extended kernel.rst and perf-security.rst documentation files with the information about CAP_PERFMON capability and its use cases - documented the case of double audit logging of CAP_PERFMON and CAP_SYS_ADMIN capabilities on a SELinux enabled system Changes in v6: - avoided noaudit checks in perfmon_capable() to explicitly advertise CAP_PERFMON usage thru audit logs to secure system performance monitoring and observability Changes in v5: - renamed CAP_SYS_PERFMON to CAP_PERFMON - extended perfmon_capable() with noaudit checks Changes in v4: - converted perfmon_capable() into an inline function - made perf_events kprobes, uprobes, hw breakpoints and namespaces data available to CAP_SYS_PERFMON privileged processes - applied perfmon_capable() to drivers/perf and drivers/oprofile - extended __cmd_ftrace() with support of CAP_SYS_PERFMON Changes in v3: - implemented perfmon_capable() macros aggregating required capabilities checks Changes in v2: - made perf_events trace points available to CAP_SYS_PERFMON privileged processes - made perf_event_paranoid_check() treat CAP_SYS_PERFMON equally to CAP_SYS_ADMIN - applied CAP_SYS_PERFMON to i915_perf, bpf_trace, powerpc and parisc system performance monitoring and observability related subsystems --- Alexey Budankov (12): capabilities: introduce CAP_PERFMON to kernel and user space perf/core: open access to the core for CAP_PERFMON privileged process perf/core: open access to probes for CAP_PERFMON privileged process perf tool: extend Perf tool with CAP_PERFMON capability support drm/i915/perf: open access for CAP_PERFMON privileged process trace/bpf_trace: open access for CAP_PERFMON privileged process powerpc/perf: open access for CAP_PERFMON privileged process parisc/perf: open access for CAP_PERFMON privileged process drivers/perf: open access for CAP_PERFMON privileged process drivers/oprofile: open access for CAP_PERFMON privileged process doc/admin-guide: update perf-security.rst with CAP_PERFMON information doc/admin-guide: update kernel.rst with CAP_PERFMON information Documentation/admin-guide/perf-security.rst | 65 +++++++++++++-------- Documentation/admin-guide/sysctl/kernel.rst | 16 +++-- arch/parisc/kernel/perf.c | 2 +- arch/powerpc/perf/imc-pmu.c | 4 +- drivers/gpu/drm/i915/i915_perf.c | 13 ++--- drivers/oprofile/event_buffer.c | 2 +- drivers/perf/arm_spe_pmu.c | 4 +- include/linux/capability.h | 4 ++ include/linux/perf_event.h | 6 +- include/uapi/linux/capability.h | 8 ++- kernel/events/core.c | 6 +- kernel/trace/bpf_trace.c | 2 +- security/selinux/include/classmap.h | 4 +- tools/perf/builtin-ftrace.c | 5 +- tools/perf/design.txt | 3 +- tools/perf/util/cap.h | 4 ++ tools/perf/util/evsel.c | 10 ++-- tools/perf/util/util.c | 1 + 18 files changed, 98 insertions(+), 61 deletions(-) --- Validation (Intel Skylake, 8 cores, Fedora 29, 5.5.0-rc3+, x86_64): libcap library [6], [7], [8] and Perf tool can be used to apply CAP_PERFMON capability for secure system performance monitoring and observability beyond the scope permitted by the system wide perf_event_paranoid kernel setting [9] and below are the steps for evaluation: - patch, build and boot the kernel - patch, build Perf tool e.g. to /home/user/perf ... # git clone git://git.kernel.org/pub/scm/libs/libcap/libcap.git libcap # pushd libcap # patch libcap/include/uapi/linux/capabilities.h with [PATCH 1] # make # pushd progs # ./setcap "cap_perfmon,cap_sys_ptrace,cap_syslog=ep" /home/user/perf # ./setcap -v "cap_perfmon,cap_sys_ptrace,cap_syslog=ep" /home/user/perf /home/user/perf: OK # ./getcap /home/user/perf /home/user/perf = cap_sys_ptrace,cap_syslog,cap_perfmon+ep # echo 2 > /proc/sys/kernel/perf_event_paranoid # cat /proc/sys/kernel/perf_event_paranoid 2 ... $ /home/user/perf top ... works as expected ... $ cat /proc/`pidof perf`/status Name: perf Umask: 0002 State: S (sleeping) Tgid: 2958 Ngid: 0 Pid: 2958 PPid: 9847 TracerPid: 0 Uid: 500 500 500 500 Gid: 500 500 500 500 FDSize: 256 ... CapInh: 0000000000000000 CapPrm: 0000004400080000 CapEff: 0000004400080000 => 01000100 00000000 00001000 00000000 00000000 cap_perfmon,cap_sys_ptrace,cap_syslog CapBnd: 0000007fffffffff CapAmb: 0000000000000000 NoNewPrivs: 0 Seccomp: 0 Speculation_Store_Bypass: thread vulnerable Cpus_allowed: ff Cpus_allowed_list: 0-7 ... Usage of cap_perfmon effectively avoids unused credentials excess: - with cap_sys_admin: CapEff: 0000007fffffffff => 01111111 11111111 11111111 11111111 11111111 - with cap_perfmon: CapEff: 0000004400080000 => 01000100 00000000 00001000 00000000 00000000 38 34 19 perfmon syslog sys_ptrace --- [1] https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html [2] http://man7.org/linux/man-pages/man7/capabilities.7.html [3] https://www.kernel.org/doc/html/latest/process/embargoed-hardware-issues.html [4] https://www.kernel.org/doc/html/latest/admin-guide/security-bugs.html [5] https://www.kernel.org/doc/html/latest/process/management-style.html#decisions [6] http://man7.org/linux/man-pages/man8/setcap.8.html [7] https://git.kernel.org/pub/scm/libs/libcap/libcap.git [8] https://sites.google.com/site/fullycapable/, posix_1003.1e-990310.pdf [9] http://man7.org/linux/man-pages/man2/perf_event_open.2.html