linux-kernel - Re: [kernel-hardening] [PATCH 2/2] security,perf: Allow further restriction of perf_event

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Message-ID: <20160617065427.GL30154@twins.programming.kicks-ass.net>
Date:	Fri, 17 Jun 2016 08:54:27 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Kees Cook <keescook@...omium.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	"linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [kernel-hardening] [PATCH 2/2] security,perf: Allow further
 restriction of perf_event_open

On Thu, Jun 16, 2016 at 03:27:55PM -0700, Kees Cook wrote:
> Hi guys,
> 
> This patch wasn't originally CCed to you (I'm fixing that now). Would
> you consider taking this into the perf tree? 

No.

> It's been in active use
> in both Debian and Android for a while now.

Very nice of you all to finally inform us I suppose :/

> >>> When kernel.perf_event_open is set to 3 (or greater), disallow all
> >>> access to performance events by users without CAP_SYS_ADMIN.
> >>> Add a Kconfig symbol CONFIG_SECURITY_PERF_EVENTS_RESTRICT that
> >>> makes this value the default.
> >>>
> >>> This is based on a similar feature in grsecurity
> >>> (CONFIG_GRKERNSEC_PERF_HARDEN).  This version doesn't include making
> >>> the variable read-only.  It also allows enabling further restriction
> >>> at run-time regardless of whether the default is changed.

This Changelog is completely devoid of information. _WHY_ are you doing
this?

Also, hate the CONFIG.