From patchwork Fri Mar 13 17:27:40 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexey Budankov X-Patchwork-Id: 11437517 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 C726613B1 for ; Fri, 13 Mar 2020 17:27:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 9CF1A20409 for ; Fri, 13 Mar 2020 17:27:53 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726446AbgCMR1x (ORCPT ); Fri, 13 Mar 2020 13:27:53 -0400 Received: from mga05.intel.com ([192.55.52.43]:6291 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726414AbgCMR1x (ORCPT ); Fri, 13 Mar 2020 13:27:53 -0400 X-Amp-Result: SKIPPED(no attachment in message) X-Amp-File-Uploaded: False Received: from orsmga002.jf.intel.com ([10.7.209.21]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 13 Mar 2020 10:27:50 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.70,549,1574150400"; d="scan'208";a="261954964" Received: from linux.intel.com ([10.54.29.200]) by orsmga002.jf.intel.com with ESMTP; 13 Mar 2020 10:27:50 -0700 Received: from [10.255.182.54] (abudanko-mobl.ccr.corp.intel.com [10.255.182.54]) by linux.intel.com (Postfix) with ESMTP id E0E9258049A; Fri, 13 Mar 2020 10:27:42 -0700 (PDT) From: Alexey Budankov Subject: [PATCH v1] perf tool: make Perf tool aware of SELinux access control Organization: Intel Corp. To: Arnaldo Carvalho de Melo Cc: Jiri Olsa , Namhyung Kim , Alexander Shishkin , Peter Zijlstra , Ingo Molnar , Andi Kleen , linux-kernel , "selinux@vger.kernel.org" , "linux-security-module@vger.kernel.org" Message-ID: Date: Fri, 13 Mar 2020 20:27:40 +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: selinux-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: selinux@vger.kernel.org Extend Perf tool with the check of /sys/fs/selinux/enforce value and notify in case access to perf_event_open() syscall is restricted by the enforced SELinux policy settings. Testing and evaluation (Fedora 31 x86_64 with enforced Targeted policy extended by perf_event class (see refpolicy [1] master branch)): [root@host ~]# ps -Z LABEL PID TTY TIME CMD unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 3960 pts/1 00:00:00 bash unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 4167 pts/1 00:00:00 ps [root@host ~]# ls -alhZ /usr/local/bin/ total 56M drwxr-xr-x. 2 root root system_u:object_r:bin_t:s0 4.0K Mar 4 12:27 . drwxr-xr-x. 12 root root system_u:object_r:usr_t:s0 4.0K Jul 25 2019 .. -rwxr-xr-x. 1 root root system_u:object_r:bin_t:s0 4.1M Jan 23 2017 bash -rwxr-xr-x. 1 root root system_u:object_r:bin_t:s0 4.1M Jan 23 2017 bash.before_shellshock_patch ... -rwxr-xr-x. 1 root root system_u:object_r:bin_t:s0 372 May 14 2019 flask -rwxr-xr-x. 1 root root unconfined_u:object_r:bin_t:s0 24M Mar 4 12:15 perf <== unprivileged users (perf_event_paranoid) -rwxr-x---. 1 root perf_users unconfined_u:object_r:bin_t:s0 24M Mar 4 12:19 perf.cap <== perf_users (CAP_SYS_ADMIN) -rwxr-xr-x. 1 root root system_u:object_r:bin_t:s0 44K Dec 8 2016 spiff ... lrwxrwxrwx. 1 root root system_u:object_r:bin_t:s0 4 Aug 21 2018 zstdmt -> zstd [root@host ~]# getenforce Enforcing === Access by unprivileged user === [user@host ~]$ ps -Z LABEL PID TTY TIME CMD unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 4043 pts/2 00:00:00 bash unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 4168 pts/2 00:00:00 ps [user@host ~]$ /usr/local/bin/perf stat -- ls Error: Access to performance monitoring and observability operations is limited. SELinux Enforcing mode is enabled and can limit access to performance monitoring and observability operations. Inspect system audit records for more perf_event access control information and adjusting the policy. Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open access to performance monitoring and observability operations for users without CAP_SYS_ADMIN capability. perf_event_paranoid setting is -1: -1: Allow use of (almost) all events by all users Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK >= 0: Disallow raw and ftrace function tracepoint access >= 1: Disallow CPU event access >= 2: Disallow kernel profiling To make the adjusted perf_event_paranoid setting permanent preserve it in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = ) [root@host ~]# journalctl --follow ... audit[4186]: AVC avc: denied { open } for pid=4186 comm="perf" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=perf_event permissive=0 ... audit[4186]: AVC avc: denied { open } for pid=4186 comm="perf" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=perf_event permissive=0 ... setroubleshoot[4194]: SELinux is preventing perf from open access on the perf_event labeled unconfined_t. For complete SELinux messages run: sealert -l 9a6f3db2-3d8f-461e-afad-0b5c3a9c3b9d ... python3[4194]: SELinux is preventing perf from open access on the perf_event labeled unconfined_t. ***** Plugin catchall (100. confidence) suggests ************************** If you believe that perf should be allowed open access on perf_event labeled unconfined_t by default. Then you should report this as a bug. You can generate a local policy module to allow this access. Do allow this access for now by executing: # ausearch -c 'perf' --raw | audit2allow -M my-perf # semodule -X 300 -i my-perf.pp === Access by perf privileged user === [user@host ~]$ ps -Z LABEL PID TTY TIME CMD unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 4043 pts/2 00:00:00 bash unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 4168 pts/2 00:00:00 ps [user@host ~]$ libcap/progs/getcap /usr/local/bin/perf.cap /usr/local/bin/perf.cap = cap_sys_ptrace,cap_syslog,cap_sys_admin+ep [user@host ~]$ /usr/local/bin/perf.cap stat -- ls Error: Access to performance monitoring and observability operations is limited. SELinux Enforcing mode is enabled and can limit access to performance monitoring and observability operations. Inspect system audit records for more perf_event access control information and adjusting the policy. Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open access to performance monitoring and observability operations for users without CAP_SYS_ADMIN capability. perf_event_paranoid setting is -1: -1: Allow use of (almost) all events by all users Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK >= 0: Disallow raw and ftrace function tracepoint access >= 1: Disallow CPU event access >= 2: Disallow kernel profiling To make the adjusted perf_event_paranoid setting permanent preserve it in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = ) [root@host ~]# journalctl --follow ... audit[3926]: AVC avc: denied { open } for pid=3926 comm="perf.cap" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=perf_event permissive=0 ... audit[3926]: AVC avc: denied { open } for pid=3926 comm="perf.cap" scontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tcontext=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 tclass=perf_event permissive=0 ... setroubleshoot[3934]: SELinux is preventing perf from open access on the perf_event labeled unconfined_t. For complete SELinux messages run: sealert -l 9a6f3db2-3d8f-461e-afad-0b5c3a9c3b9d ... python3[3934]: SELinux is preventing perf from open access on the perf_event labeled unconfined_t. ***** Plugin catchall (100. confidence) suggests ************************** If you believe that perf should be allowed open access on perf_event labeled unconfined_t by default. Then you should report this as a bug. You can generate a local policy module to allow this access. Do allow this access for now by executing: # ausearch -c 'perf' --raw | audit2allow -M my-perf # semodule -X 300 -i my-perf.pp === Open access to performance monitoring and observability operations in unconfined_t domain === [root@host ~]# ausearch -c 'perf' --raw | audit2allow -M my-perf && cat my-perf.te module my-perf 1.0; require { type unconfined_t; class perf_event { cpu kernel open read tracepoint write }; } #============= unconfined_t ============== allow unconfined_t self:perf_event { cpu kernel open read tracepoint write }; [root@host ~]# semodule -X 300 -i my-perf.pp [user@host ~]$ ps -Z LABEL PID TTY TIME CMD unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 4043 pts/2 00:00:00 bash unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 4168 pts/2 00:00:00 ps [user@host ~]$ /usr/local/bin/perf stat -- ls Desktop Documents Downloads intel Music perf.data perf.data.old Pictures Public Templates Videos Performance counter stats for 'ls': 0.72 msec task-clock:u # 0.655 CPUs utilized 0 context-switches:u # 0.000 K/sec 0 cpu-migrations:u # 0.000 K/sec 98 page-faults:u # 0.137 M/sec 908,356 cycles:u # 1.266 GHz 729,984 instructions:u # 0.80 insn per cycle 142,774 branches:u # 198.968 M/sec 8,238 branch-misses:u # 5.77% of all branches 0.001095239 seconds time elapsed 0.001147000 seconds user 0.000000000 seconds sys [user@host ~]$ /usr/local/bin/perf stat -a Error: Access to performance monitoring and observability operations is limited. SELinux Enforcing mode is enabled and can limit access to performance monitoring and observability operations. Inspect system audit records for more perf_event access control information and adjusting the policy. Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open access to performance monitoring and observability operations for users without CAP_SYS_ADMIN capability. perf_event_paranoid setting is -1: -1: Allow use of (almost) all events by all users Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK >= 0: Disallow raw and ftrace function tracepoint access >= 1: Disallow CPU event access >= 2: Disallow kernel profiling To make the adjusted perf_event_paranoid setting permanent preserve it in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = ) [user@host ~]$ /usr/local/bin/perf.cap stat -a ^C Performance counter stats for 'system wide': 13,427.05 msec cpu-clock # 7.997 CPUs utilized 783 context-switches # 0.058 K/sec 29 cpu-migrations # 0.002 K/sec 6 page-faults # 0.000 K/sec 161,084,874 cycles # 0.012 GHz 146,823,131 instructions # 0.91 insn per cycle 12,164,802 branches # 0.906 M/sec 380,350 branch-misses # 3.13% of all branches 1.678938906 seconds time elapsed [1] https://github.com/SELinuxProject/refpolicy Signed-off-by: Alexey Budankov --- tools/perf/util/cloexec.c | 4 ++-- tools/perf/util/evsel.c | 40 +++++++++++++++++++++++---------------- 2 files changed, 26 insertions(+), 18 deletions(-) diff --git a/tools/perf/util/cloexec.c b/tools/perf/util/cloexec.c index a12872f2856a..9c8ec816261b 100644 --- a/tools/perf/util/cloexec.c +++ b/tools/perf/util/cloexec.c @@ -65,7 +65,7 @@ static int perf_flag_probe(void) return 1; } - WARN_ONCE(err != EINVAL && err != EBUSY, + WARN_ONCE(err != EINVAL && err != EBUSY && err != EACCES, "perf_event_open(..., PERF_FLAG_FD_CLOEXEC) failed with unexpected error %d (%s)\n", err, str_error_r(err, sbuf, sizeof(sbuf))); @@ -83,7 +83,7 @@ static int perf_flag_probe(void) if (fd >= 0) close(fd); - if (WARN_ONCE(fd < 0 && err != EBUSY, + if (WARN_ONCE(fd < 0 && err != EBUSY && err != EACCES, "perf_event_open(..., 0) failed unexpectedly with error %d (%s)\n", err, str_error_r(err, sbuf, sizeof(sbuf)))) return -1; diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 816d930d774e..f03ce1d362d3 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -2493,32 +2493,40 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target, int err, char *msg, size_t size) { char sbuf[STRERR_BUFSIZE]; - int printed = 0; + int printed = 0, enforced = 0; switch (err) { case EPERM: case EACCES: + printed += scnprintf(msg + printed, size - printed, + "Access to performance monitoring and observability operations is limited.\n"); + + if (!sysfs__read_int("fs/selinux/enforce", &enforced)) { + if (enforced) { + printed += scnprintf(msg + printed, size - printed, + "SELinux Enforcing mode is enabled and can limit access to performance\n" + "monitoring and observability operations. Inspect system audit records\n" + "for more perf_event access control information and adjusting the policy.\n"); + } + } + if (err == EPERM) - printed = scnprintf(msg, size, - "No permission to enable %s event.\n\n", + printed += scnprintf(msg, size, + "No permission to enable %s event.\n", perf_evsel__name(evsel)); return scnprintf(msg + printed, size - printed, - "You may not have permission to collect %sstats.\n\n" - "Consider tweaking /proc/sys/kernel/perf_event_paranoid,\n" - "which controls use of the performance events system by\n" - "unprivileged users (without CAP_SYS_ADMIN).\n\n" - "The current value is %d:\n\n" + "Consider adjusting /proc/sys/kernel/perf_event_paranoid setting to open\n" + "access to performance monitoring and observability operations for users\n" + "without CAP_SYS_ADMIN capability. perf_event_paranoid setting is %d:\n" " -1: Allow use of (almost) all events by all users\n" " Ignore mlock limit after perf_event_mlock_kb without CAP_IPC_LOCK\n" - ">= 0: Disallow ftrace function tracepoint by users without CAP_SYS_ADMIN\n" - " Disallow raw tracepoint access by users without CAP_SYS_ADMIN\n" - ">= 1: Disallow CPU event access by users without CAP_SYS_ADMIN\n" - ">= 2: Disallow kernel profiling by users without CAP_SYS_ADMIN\n\n" - "To make this setting permanent, edit /etc/sysctl.conf too, e.g.:\n\n" - " kernel.perf_event_paranoid = -1\n" , - target->system_wide ? "system-wide " : "", - perf_event_paranoid()); + ">= 0: Disallow raw and ftrace function tracepoint access\n" + ">= 1: Disallow CPU event access\n" + ">= 2: Disallow kernel profiling\n" + "To make the adjusted perf_event_paranoid setting permanent preserve it\n" + "in /etc/sysctl.conf (e.g. kernel.perf_event_paranoid = )", + perf_event_paranoid()); case ENOENT: return scnprintf(msg, size, "The %s event is not supported.", perf_evsel__name(evsel));