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Date:   Mon, 19 Nov 2018 11:33:37 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     Alexey Budankov <alexey.budankov@linux.intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Kees Cook <keescook@chromium.org>,
        Jann Horn <jannh@google.com>, Ingo Molnar <mingo@redhat.com>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Andi Kleen <ak@linux.intel.com>,
        Jonatan Corbet <corbet@lwn.net>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@redhat.com>,
        Namhyung Kim <namhyung@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>,
        Tvrtko Ursulin <tursulin@ursulin.net>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        kernel-hardening@lists.openwall.com, linux-doc@vger.kernel.org
Subject: Re: [PATCH v1 2/2]: Documentation/admin-guide: introduce
 perf-security.rst file
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On Mon, Nov 19, 2018 at 08:42:52AM +0300, Alexey Budankov wrote:
> 
> Implement initial version of perf-security.rst documentation file 
> initially covering security concerns related to PCL/Perf performance 
> monitoring in multiuser environments.

Ditch the PCL thing. That's not a term used anywhere in the kernel.

Also:

> +PCL/Perf unprivileged users
> +---------------------------
> +
> +PCL/Perf *scope* and *access* control for unprivileged processes is governed by
> +perf_event_paranoid [2]_ setting:
> +
> +**-1**:
> +     Impose no *scope* and *access* restrictions on using PCL performance
> +     monitoring. Per-user per-cpu perf_event_mlock_kb [2]_ 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 PCL 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 [6]_ 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.
> +
> +**>=3**:
> +     Restrict *access* to PCL performance monitoring for unprivileged processes.
> +     This is the default on Debian and Android [7]_ , [8]_ .

that ** crud is unreadable.

http://lkml.kernel.org/r/094556ca-ea87-9c4a-2115-600d2833fb2a@darmarit.de