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Date:   Sun, 1 Mar 2020 18:19:13 -0600
From:   Serge Hallyn <serge@hallyn.com>
To:     Alexey Budankov <alexey.budankov@linux.intel.com>
Cc:     James Morris <jmorris@namei.org>,
        Stephen Smalley <sds@tycho.nsa.gov>,
        Peter Zijlstra <peterz@infradead.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        "joonas.lahtinen@linux.intel.com" <joonas.lahtinen@linux.intel.com>,
        Alexei Starovoitov <ast@kernel.org>,
        Will Deacon <will@kernel.org>,
        Paul Mackerras <paulus@samba.org>,
        Helge Deller <deller@gmx.de>,
        Thomas Gleixner <tglx@linutronix.de>,
        linux-man@vger.kernel.org, Andi Kleen <ak@linux.intel.com>,
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        Stephane Eranian <eranian@google.com>,
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        <linux-security-module@vger.kernel.org>,
        oprofile-list@lists.sf.net, Jiri Olsa <jolsa@redhat.com>,
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Subject: Re: [Intel-gfx] [PATCH v7 00/12] Introduce CAP_PERFMON to secure
 system performance monitoring and observability
Message-ID: <20200302001913.GA21145@sl>
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Thanks, this looks good to me, in keeping with the CAP_SYSLOG break.

Acked-by: Serge E. Hallyn <serge@hallyn.com>

for the set.

James/Ingo/Peter, if noone has remaining objections, whose branch
should these go in through?

thanks,
-serge

On Tue, Feb 25, 2020 at 12:55:54PM +0300, Alexey Budankov wrote:
> 
> Hi,
> 
> Is there anything else I could do in order to move the changes forward
> or is something still missing from this patch set?
> Could you please share you mind?
> 
> Thanks,
> Alexey
> 
> On 17.02.2020 11:02, Alexey Budankov wrote:
> > 
> > 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
> > 
> > ---
> > 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
> > 
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