linux-kernel - [PATCH 0/3] perf: Use capabilities instead of uid and euid

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Date:   Tue, 2 Jul 2019 20:10:02 -0400
From:   Igor Lubashev <ilubashe@...mai.com>
To:     <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>
CC:     Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        <linux-arm-kernel@...ts.infradead.org>,
        James Morris <jmorris@...ei.org>,
        Igor Lubashev <ilubashe@...mai.com>
Subject: [PATCH 0/3] perf: Use capabilities instead of uid and euid

Kernel is using capabilities instead of uid and euid to restrict access to
kernel pointers and tracing facilities.  This patch series updates the perf to
better match the security model used by the kernel.

This series enables instructions in Documentation/admin-guide/perf-security.rst
to actually work, even when kernel.perf_event_paranoid=2 and
kernel.kptr_restrict=1.

The series consists of three patches:

  01: perf: Add capability-related utilities
    Add utility functions to check capabilities and perf_event_paranoid checks.

  02: perf: Use CAP_SYS_ADMIN with perf_event_paranoid checks
    Replace the use of euid==0 with a check for CAP_SYS_ADMIN whenever
    perf_event_paranoid level is verified.

  03: perf: Use CAP_SYSLOG with kptr_restrict checks
    Replace the use of uid and euid with a check for CAP_SYSLOG when
    kptr_restrict is verified (similar to kernel/kallsyms.c and lib/vsprintf.c).
    Consult perf_event_paranoid when kptr_restrict==0 (see kernel/kallsyms.c).

I tested this by following Documentation/admin-guide/perf-security.rst
guidelines and setting sysctls:

   kernel.perf_event_paranoid=2
   kernel.kptr_restrict=1

As an unpriviledged user who is in perf_users group (setup via instructions
above), I executed:
   perf record -a -- sleep 1

Without the patch, perf record did not capture any kernel functions.
With the patch, perf included all kernel funcitons.

Igor Lubashev (3):
  perf: Add capability-related utilities
  perf: Use CAP_SYS_ADMIN with perf_event_paranoid checks
  perf: Use CAP_SYSLOG with kptr_restrict checks

 tools/perf/Makefile.config           |  2 +-
 tools/perf/arch/arm/util/cs-etm.c    |  3 ++-
 tools/perf/arch/arm64/util/arm-spe.c |  3 ++-
 tools/perf/arch/x86/util/intel-bts.c |  3 ++-
 tools/perf/arch/x86/util/intel-pt.c  |  2 +-
 tools/perf/util/Build                |  1 +
 tools/perf/util/cap.c                | 24 ++++++++++++++++++++++++
 tools/perf/util/cap.h                | 10 ++++++++++
 tools/perf/util/event.h              |  1 +
 tools/perf/util/evsel.c              |  2 +-
 tools/perf/util/python-ext-sources   |  1 +
 tools/perf/util/symbol.c             | 15 +++++++++++----
 tools/perf/util/util.c               |  9 +++++++++
 13 files changed, 66 insertions(+), 10 deletions(-)
 create mode 100644 tools/perf/util/cap.c
 create mode 100644 tools/perf/util/cap.h

-- 
2.7.4