[Intel-gfx] [PATCH v7 00/12] Introduce CAP_PERFMON to secure system performance monitoring and observability
Serge Hallyn
serge at hallyn.com
Mon Mar 2 11:19:13 AEDT 2020
Thanks, this looks good to me, in keeping with the CAP_SYSLOG break.
Acked-by: Serge E. Hallyn <serge at 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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