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From: Mark Rutland <mark.rutland@arm.com>
To: kernel-hardening@lists.openwall.com
Cc: peterz@infradead.org, mingo@redhat.com, acme@kernel.org,
	alexander.shishkin@linux.intel.com, linux-doc@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	Jeff Vander Stoep <jeffv@google.com>
Subject: Re: [kernel-hardening] [PATCH 1/2] security, perf: allow further restriction of perf_event_open
Date: Mon, 17 Oct 2016 14:44:14 +0100
Message-ID: <20161017134413.GK29095@leverpostej> (raw)
In-Reply-To: <1469630746-32279-1-git-send-email-jeffv@google.com>

Hi,

Attempt to revive discussions below...

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. 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].
> 
> This feature is derived from CONFIG_GRKERNSEC_PERF_HARDEN by Brad
> Spengler. It is based on a patch by Ben Hutchings [2]. Ben's patches
> have been modified and split up to address on-list feedback.
> 
> kernel.perf_event_paranoid=3 is the default on both Debian [2] and
> Android [3].

While people weren't particularly happy with this global toggle
approach, my understanding from face-to-face discussions at LSS2016 was
that people were happy with a more scoped restriction (e.g. using
capabilities or some other access control mechanism), but no-one had the
time to work on that.

Does that match everyone's understanding, or am I mistaken?

It's also my understanding that for Android, perf_event_paranoid is
lowered when the user enables developer mode (rather than only when an
external debugger is attached); is that correct?

Thanks,
Mark.

  parent reply index

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-07-27 14:45 Jeff Vander Stoep
2016-07-27 20:43 ` Kees Cook
2016-08-02  9:52 ` [kernel-hardening] " Peter Zijlstra
2016-08-02 13:04   ` Arnaldo Carvalho de Melo
2016-08-02 13:10     ` Daniel Micay
2016-08-02 13:16   ` Daniel Micay
2016-08-02 19:04   ` Kees Cook
2016-08-02 20:30     ` Peter Zijlstra
2016-08-02 20:51       ` Kees Cook
2016-08-02 21:06         ` Jeffrey Vander Stoep
2016-08-03  8:28         ` Ingo Molnar
2016-08-03 12:28           ` Daniel Micay
2016-08-03 12:53             ` Daniel Micay
2016-08-03 13:36             ` Peter Zijlstra
2016-08-03 14:41         ` Peter Zijlstra
2016-08-03 15:42           ` Schaufler, Casey
2016-08-03 17:25         ` Eric W. Biederman
2016-08-03 18:53           ` Kees Cook
2016-08-03 21:44             ` Peter Zijlstra
2016-08-04  2:50               ` Eric W. Biederman
2016-08-04  9:11                 ` Peter Zijlstra
2016-08-04 15:13                   ` Eric W. Biederman
2016-08-04 15:37                     ` Peter Zijlstra
2016-08-03 19:36           ` Daniel Micay
2016-08-04 10:28             ` Mark Rutland
2016-08-04 13:45               ` Daniel Micay
2016-08-04 14:11                 ` Peter Zijlstra
2016-08-04 15:44                   ` Daniel Micay
2016-08-04 15:55                     ` Peter Zijlstra
2016-08-04 16:10                     ` Mark Rutland
2016-08-04 16:32                       ` Daniel Micay
2016-08-04 17:09                         ` Mark Rutland
2016-08-04 17:36                           ` Daniel Micay
2016-08-02 21:16       ` Jeffrey Vander Stoep
2016-10-17 13:44 ` Mark Rutland [this message]
2016-10-17 14:54   ` [kernel-hardening] " Daniel Micay
2016-10-19  9:41     ` Mark Rutland
2016-10-19 15:16       ` Daniel Micay
2016-10-18 20:48   ` Kees Cook
2016-10-18 21:15     ` Daniel Micay
2016-10-19  9:56       ` Mark Rutland
2016-10-19 10:01       ` Peter Zijlstra
2016-10-19 10:26         ` Arnaldo Carvalho de Melo
2016-10-19 10:40           ` Peter Zijlstra
2016-10-19 15:39           ` Daniel Micay

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