linux-kernel - [PATCH v2 3/7] perf tool: extend Perf tool with CAP_SYS

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Message-ID: <40b9755f-bcbd-c096-37f0-ab2f50393f06@linux.intel.com>
Date:   Mon, 16 Dec 2019 10:16:19 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>, jani.nikula@...ux.intel.com,
        joonas.lahtinen@...ux.intel.com, rodrigo.vivi@...el.com,
        Alexei Starovoitov <ast@...nel.org>,
        james.bottomley@...senpartnership.com, benh@...nel.crashing.org,
        Casey Schaufler <casey@...aufler-ca.com>, serge@...lyn.com,
        James Morris <jmorris@...ei.org>
Cc:     Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Igor Lubashev <ilubashe@...mai.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Jann Horn <jannh@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>,
        linux-security-module@...r.kernel.org, selinux@...r.kernel.org,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        intel-gfx@...ts.freedesktop.org, bgregg@...flix.com,
        Song Liu <songliubraving@...com>, bpf@...r.kernel.org,
        linux-parisc@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org
Subject: [PATCH v2 3/7] perf tool: extend Perf tool with CAP_SYS_PERFMON
 capability support


Extend error messages to mention CAP_SYS_PERFMON capability as an option
to substitute CAP_SYS_ADMIN capability for secure system performance
monitoring and observability operations [1]. Make perf_event_paranoid_check()
to be aware of CAP_SYS_PERFMON capability.

[1] https://www.kernel.org/doc/html/latest/admin-guide/perf-security.html

Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
---
 tools/perf/design.txt   |  3 ++-
 tools/perf/util/cap.h   |  4 ++++
 tools/perf/util/evsel.c | 10 +++++-----
 tools/perf/util/util.c  |  1 +
 4 files changed, 12 insertions(+), 6 deletions(-)

diff --git a/tools/perf/design.txt b/tools/perf/design.txt
index 0453ba26cdbd..71755b3e1303 100644
--- a/tools/perf/design.txt
+++ b/tools/perf/design.txt
@@ -258,7 +258,8 @@ gets schedule to. Per task counters can be created by any user, for
 their own tasks.
 
 A 'pid == -1' and 'cpu == x' counter is a per CPU counter that counts
-all events on CPU-x. Per CPU counters need CAP_SYS_ADMIN privilege.
+all events on CPU-x. Per CPU counters need CAP_SYS_PERFMON or
+CAP_SYS_ADMIN privilege.
 
 The 'flags' parameter is currently unused and must be zero.
 
diff --git a/tools/perf/util/cap.h b/tools/perf/util/cap.h
index 051dc590ceee..0f79fbf6638b 100644
--- a/tools/perf/util/cap.h
+++ b/tools/perf/util/cap.h
@@ -29,4 +29,8 @@ static inline bool perf_cap__capable(int cap __maybe_unused)
 #define CAP_SYSLOG	34
 #endif
 
+#ifndef CAP_SYS_PERFMON
+#define CAP_SYS_PERFMON 38
+#endif
+
 #endif /* __PERF_CAP_H */
diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c
index f4dea055b080..3a46325e3702 100644
--- a/tools/perf/util/evsel.c
+++ b/tools/perf/util/evsel.c
@@ -2468,14 +2468,14 @@ int perf_evsel__open_strerror(struct evsel *evsel, struct target *target,
 		 "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"
+		 "unprivileged users (without CAP_SYS_PERFMON or CAP_SYS_ADMIN).\n\n"
 		 "The current value is %d:\n\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"
+		 ">= 0: Disallow ftrace function tracepoint by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
+		 "      Disallow raw tracepoint access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
+		 ">= 1: Disallow CPU event access by users without CAP_SYS_PERFMON or CAP_SYS_ADMIN\n"
+		 ">= 2: Disallow kernel profiling by users without CAP_SYS_PERFMON or 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 " : "",
diff --git a/tools/perf/util/util.c b/tools/perf/util/util.c
index 969ae560dad9..9981db0d8d09 100644
--- a/tools/perf/util/util.c
+++ b/tools/perf/util/util.c
@@ -272,6 +272,7 @@ int perf_event_paranoid(void)
 bool perf_event_paranoid_check(int max_level)
 {
 	return perf_cap__capable(CAP_SYS_ADMIN) ||
+			perf_cap__capable(CAP_SYS_PERFMON) ||
 			perf_event_paranoid() <= max_level;
 }
 
-- 
2.20.1