Date: Mon, 19 Nov 2018 18:13:16 +0300 From: Alexey Budankov <alexey.budankov@...ux.intel.com> To: Peter Zijlstra <peterz@...radead.org> Cc: Thomas Gleixner <tglx@...utronix.de>, Kees Cook <keescook@...omium.org>, Jann Horn <jannh@...gle.com>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Andi Kleen <ak@...ux.intel.com>, Jonatan Corbet <corbet@....net>, 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, linux-doc@...r.kernel.org Subject: Re: [PATCH v1 2/2]: Documentation/admin-guide: introduce perf-security.rst file Hi, On 19.11.2018 13:33, Peter Zijlstra wrote: > 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. Ok. Which is the proper wording to reference to Perf kernel subsystem? > > Also: > >> +PCL/Perf unprivileged users >> +--------------------------- >> + >> +PCL/Perf *scope* and *access* control for unprivileged processes is governed by >> +perf_event_paranoid _ setting: >> + >> +**-1**: >> + Impose no *scope* and *access* restrictions on using PCL 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 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 _ 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 _ , _ . > > that ** crud is unreadable. It can be avoided without missing the sense. "two asterisks: **text** for strong emphasis (boldface)". Thanks, Alexey > > http://email@example.com >
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