Date: Tue, 20 Nov 2018 12:27:55 +0300 From: Alexey Budankov <alexey.budankov@...ux.intel.com> To: Thomas Gleixner <tglx@...utronix.de>, Kees Cook <keescook@...omium.org>, Jann Horn <jannh@...gle.com>, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Arnaldo Carvalho de Melo <acme@...nel.org>, Andi Kleen <ak@...ux.intel.com>, Jonatan Corbet <corbet@....net> Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, Tvrtko Ursulin <tursulin@...ulin.net>, linux-kernel <linux-kernel@...r.kernel.org>, "kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>, "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org> Subject: [PATCH v2 1/2] Documentation/admin-guide: introduce perf-security.rst file Implement initial version of perf-security.rst documentation file initially covering security concerns related to PE/Perf performance monitoring in multiuser environments. Suggested-by: Thomas Gleixner <tglx@...utronix.de> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com> --- Changes in v2: - replaced old PCL referencing by PE (Perf Events) - skipped >=3 setting documentation at the moment --- Documentation/admin-guide/perf-security.rst | 76 +++++++++++++++++++++ 1 file changed, 76 insertions(+) create mode 100644 Documentation/admin-guide/perf-security.rst diff --git a/Documentation/admin-guide/perf-security.rst b/Documentation/admin-guide/perf-security.rst new file mode 100644 index 000000000000..d9dcea61ed87 --- /dev/null +++ b/Documentation/admin-guide/perf-security.rst @@ -0,0 +1,76 @@ +.. _perf_security: + +Perf Events and tool security +============================= + +Overview +-------- + +Usage of Perf Events (PE) _ , _ , _ can impose a considerable risk of +leaking sensitive data accessed by monitored processes. The data leakage is +possible both in scenarios of direct usage of PE system call API _ and over +data files generated by Perf tool user mode utility (Perf) _ , _ . The risk +depends on the nature of data that PE performance monitoring units (PMU) _ +collect and expose for performance analysis. Having that said PE/Perf performance +monitoring is the subject for security access control management _ . + +PE/Perf access control +---------------------- + +For the purpose of performing security checks Linux implementation splits +processes into two categories _ : a) privileged processes (whose effective +user ID is 0, referred to as superuser or root), and b) unprivileged processes +(whose effective UID is nonzero). Privileged processes bypass all kernel +security permission checks so PE performance monitoring is fully available to +privileged processes without *access*, *scope* and *resource* restrictions. +Unprivileged processes are subject to full security permission check based +on the process's credentials _ (usually: effective UID, effective GID, +and supplementary group list). + +PE/Perf unprivileged users +-------------------------- + +PE/Perf *scope* and *access* control for unprivileged processes is governed by +perf_event_paranoid _ setting: + +-1: + Impose no *scope* and *access* restrictions on using PE performance + monitoring. Per-user per-cpu perf_event_mlock_kb _ locking limit is + ignored when allocating memory buffers for storing performance data. + This is the least secure mode since allowed monitored *scope* is + maximized and no PE specific limits are imposed on *resources* + allocated for performance monitoring. + +>=0: + *scope* includes per-process and system wide performance monitoring + but excludes raw tracepoints and ftrace function tracepoints monitoring. + CPU and system events happened when executing either in user or + in kernel space can be monitored and captured for later analysis. + Per-user per-cpu perf_event_mlock_kb locking limit is imposed but + ignored for unprivileged processes with CAP_IPC_LOCK _ capability. + +>=1: + *scope* includes per-process performance monitoring only and excludes + system wide performance monitoring. CPU and system events happened when + executing either in user or in kernel space can be monitored and + captured for later analysis. Per-user per-cpu perf_event_mlock_kb + locking limit is imposed but ignored for unprivileged processes with + CAP_IPC_LOCK capability. + +>=2: + *scope* includes per-process performance monitoring only. CPU and system + events happened when executing in user space only can be monitored and + captured for later analysis. Per-user per-cpu perf_event_mlock_kb + locking limit is imposed but ignored for unprivileged processes with + CAP_IPC_LOCK capability. + +Bibliography +------------ + +..  `<https://lwn.net/Articles/337493/>`_ +..  `<http://man7.org/linux/man-pages/man2/perf_event_open.2.html>`_ +..  `<http://web.eece.maine.edu/~vweaver/projects/perf_events/>`_ +..  `<https://perf.wiki.kernel.org/index.php/Main_Page>`_ +..  `<https://www.kernel.org/doc/html/latest/security/credentials.html>`_ +..  `<http://man7.org/linux/man-pages/man7/capabilities.7.html>`_ +
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