linux-kernel - Re: [PATCH 1/2] security, perf: allow further restriction of perf_event

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Date:	Tue, 2 Aug 2016 11:52:43 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Jeff Vander Stoep <jeffv@...gle.com>
Cc:	kernel-hardening@...ts.openwall.com, mingo@...hat.com,
	acme@...nel.org, alexander.shishkin@...ux.intel.com,
	linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] security, perf: allow further restriction of
 perf_event_open

On Wed, Jul 27, 2016 at 07:45:46AM -0700, Jeff Vander Stoep wrote:
> When kernel.perf_event_paranoid is set to 3 (or greater), disallow
> all access to performance events by users without CAP_SYS_ADMIN.
> 
> This new level of restriction is intended to reduce the attack
> surface of the kernel. Perf is a valuable tool for developers but
> is generally unnecessary and unused on production systems. Perf may
> open up an attack vector to vulnerable device-specific drivers as
> recently demonstrated in CVE-2016-0805, CVE-2016-0819,
> CVE-2016-0843, CVE-2016-3768, and CVE-2016-3843.

We have bugs we fix them, we don't kill complete infrastructure because
of them.

> This new level of
> restriction allows for a safe default to be set on production systems
> while leaving a simple means for developers to grant access [1].

So the problem I have with this is that it will completely inhibit
development of things like JITs that self-profile to re-compile
frequently used code.

I would much rather have an LSM hook where the security stuff can do
more fine grained control of things. Allowing some apps perf usage while
denying others.