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Re: [PATCH 2/2] security,perf: Allow further restriction of perf_event_open

Started byAlexander Shishkin <alexander.shishkin@linux.intel.com>
First post2016-06-17 08:00 +0200
Last post2016-06-17 17:30 +0200
Articles 3 — 3 participants

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  Re: [PATCH 2/2] security,perf: Allow further restriction of perf_event_open Alexander Shishkin <alexander.shishkin@linux.intel.com> - 2016-06-17 08:00 +0200
    Re: [PATCH 2/2] security,perf: Allow further restriction of  perf_event_open Ben Hutchings <ben@decadent.org.uk> - 2016-06-17 14:20 +0200
    Re: [kernel-hardening] Re: [PATCH 2/2] security,perf: Allow further  restriction of perf_event_open Daniel Micay <danielmicay@gmail.com> - 2016-06-17 17:30 +0200

#1424686 — Re: [PATCH 2/2] security,perf: Allow further restriction of perf_event_open

FromAlexander Shishkin <alexander.shishkin@linux.intel.com>
Date2016-06-17 08:00 +0200
SubjectRe: [PATCH 2/2] security,perf: Allow further restriction of perf_event_open
Message-ID<rKUYV-2vY-5@gated-at.bofh.it>
Ben Hutchings <ben@decadent.org.uk> writes:

> 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.

So this patch does two things, can it then be made into two patches?

>
> 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 paragraph doesn't seem to belong in the commit message.

What this commit message is missing entirely is the rationale behind
this change other than "grsecurity does the same". Can you please
elaborate?

> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> ---
> I made a similar change to Debian's kernel packages in August,
> including the more restrictive default, and no-one has complained yet.

As a debian user, is this a good place to complain? Because it does get
it the way.

Thanks,
--
Alex

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#1424999 — Re: [PATCH 2/2] security,perf: Allow further restriction of perf_event_open

FromBen Hutchings <ben@decadent.org.uk>
Date2016-06-17 14:20 +0200
SubjectRe: [PATCH 2/2] security,perf: Allow further restriction of perf_event_open
Message-ID<rL0UF-6pR-3@gated-at.bofh.it>
In reply to#1424686

[Multipart message — attachments visible in raw view] — view raw

On Fri, 2016-06-17 at 08:56 +0300, Alexander Shishkin wrote:
> Ben Hutchings <ben@decadent.org.uk> writes:
> 
> > 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.
> 
> So this patch does two things, can it then be made into two patches?

It could.

> > 
> > 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 paragraph doesn't seem to belong in the commit message.

I'm giving credit where credit is due.

> What this commit message is missing entirely is the rationale behind
> this change other than "grsecurity does the same". Can you please
> elaborate?

It allows disabling a facility which in many systems is not needed and
is only a security risk.

> > Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
> > ---
> > I made a similar change to Debian's kernel packages in August,
> > including the more restrictive default, and no-one has complained yet.
> 
> As a debian user, is this a good place to complain? Because it does get
> it the way.

OK, then you're the first one.  And you know how to change this, don't
you?

Ben.

-- 
Ben Hutchings
We get into the habit of living before acquiring the habit of thinking.
                                                              - Albert
Camus

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#1425221 — Re: [kernel-hardening] Re: [PATCH 2/2] security,perf: Allow further restriction of perf_event_open

FromDaniel Micay <danielmicay@gmail.com>
Date2016-06-17 17:30 +0200
SubjectRe: [kernel-hardening] Re: [PATCH 2/2] security,perf: Allow further restriction of perf_event_open
Message-ID<rL3Sx-8fe-17@gated-at.bofh.it>
In reply to#1424686

[Multipart message — attachments visible in raw view] — view raw

> As a debian user, is this a good place to complain? Because it does
> get
> it the way.

It would be relevant to whether or not it should be set to 3 by default
in the kernel without explicit configuration, but there's no proposal to
do that. Debian has to pick a trade-off beyond security and a tiny
roadblock for developers. It's not always the case though.

In Android, there's userspace integration allowing it to be toggled by
the Android Debugging Bridge shell user so profiling tools are being
taught to automatically toggle it. Enabling ADB and then using it for
profiling is an implicit opt-in.

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