From: Mark Rutland <mark.rutland@arm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Tvrtko Ursulin <tursulin@ursulin.net>,
LKML <linux-kernel@vger.kernel.org>,
tvrtko.ursulin@linux.intel.com,
Peter Zijlstra <peterz@infradead.org>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Jiri Olsa <jolsa@redhat.com>, Namhyung Kim <namhyung@kernel.org>,
Madhavan Srinivasan <maddy@linux.vnet.ibm.com>,
Andi Kleen <ak@linux.intel.com>,
Alexey Budankov <alexey.budankov@linux.intel.com>,
Kees Cook <keescook@chromium.org>, Jann Horn <jannh@google.com>
Subject: Re: [RFC 0/5] perf: Per PMU access controls (paranoid setting)
Date: Fri, 28 Sep 2018 17:41:11 +0100 [thread overview]
Message-ID: <20180928164111.i6nba2j6mnegwslw@lakrids.cambridge.arm.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1809281151190.2004@nanos.tec.linutronix.de>
On Fri, Sep 28, 2018 at 12:26:52PM +0200, Thomas Gleixner wrote:
> On Wed, 19 Sep 2018, Tvrtko Ursulin wrote:
>
> It would be very helpful if you cc all involved people on the cover letter
> instead of just cc'ing your own pile of email addresses. CC'ed now.
>
> > For situations where sysadmins might want to allow different level of
> > access control for different PMUs, we start creating per-PMU
> > perf_event_paranoid controls in sysfs.
> >
> > These work in equivalent fashion as the existing perf_event_paranoid
> > sysctl, which now becomes the parent control for each PMU.
> >
> > On PMU registration the global/parent value will be inherited by each PMU,
> > as it will be propagated to all registered PMUs when the sysctl is
> > updated.
> >
> > At any later point individual PMU access controls, located in
> > <sysfs>/device/<pmu-name>/perf_event_paranoid, can be adjusted to achieve
> > fine grained access control.
> >
> > Discussion from previous posting:
> > https://lkml.org/lkml/2018/5/21/156
>
> This is really not helpful. The cover letter and the change logs should
> contain a summary of that discussion and a proper justification of the
> proposed change. Just saying 'sysadmins might want to allow' is not useful
> at all, it's yet another 'I want a pony' thing.
>
> I read through the previous thread and there was a clear request to involve
> security people into this. Especially those who are deeply involved with
> hardware side channels. I don't see anyone Cc'ed on the whole series.
>
> For the record, I'm not buying the handwavy 'more noise' argument at
> all. It wants a proper analysis and we need to come up with criteria which
> PMUs can be exposed at all.
>
> All of this want's a proper documentation clearly explaining the risks and
> scope of these knobs per PMU. Just throwing magic knobs at sysadmins and
> then saying 'its their problem to figure it out' is not acceptable.
There's also been prior discussion on these feature in other contexts
(e.g. android expoits resulting from out-of-tree drivers). It would be
nice to see those considered.
IIRC The conclusion from prior discussions (e.g. [1]) was that we wanted
finer granularity of control such that we could limit PMU access to
specific users -- e.g. disallow arbitrary android apps from poking *any*
PMU, while allowing some more trusted apps/users to uses *some* specific
PMUs.
e.g. we could add /sys/bus/event_source/devices/${PMU}/device, protect
this via the usual fs ACLs, and pass the fd to perf_event_open()
somehow. A valid fd would act as a capability, taking precedence over
perf_event_paranoid.
Thanks,
Mark.
[1] https://patchwork.kernel.org/patch/9249919/
next prev parent reply other threads:[~2018-09-28 16:41 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-19 12:27 [RFC 0/5] perf: Per PMU access controls (paranoid setting) Tvrtko Ursulin
2018-09-19 12:27 ` [RFC 1/5] perf: Move some access checks later in perf_event_open Tvrtko Ursulin
2018-09-19 12:27 ` [RFC 2/5] perf: Pass pmu pointer to perf_paranoid_* helpers Tvrtko Ursulin
2018-09-19 12:27 ` [RFC 3/5] perf: Allow per PMU access control Tvrtko Ursulin
2018-09-27 20:15 ` Andi Kleen
2018-09-28 8:57 ` Tvrtko Ursulin
2018-09-19 12:27 ` [RFC 4/5] perf Documentation: Document the per PMU perf_event_paranoid interface Tvrtko Ursulin
2018-09-19 12:27 ` [RFC 5/5] tools/perf: Add support for per-PMU access control Tvrtko Ursulin
2018-09-28 10:26 ` [RFC 0/5] perf: Per PMU access controls (paranoid setting) Thomas Gleixner
2018-09-28 13:22 ` Tvrtko Ursulin
2018-09-28 14:02 ` Thomas Gleixner
2018-09-28 14:56 ` Tvrtko Ursulin
2018-09-28 15:23 ` Thomas Gleixner
2018-09-28 15:45 ` Alexey Budankov
2018-09-28 18:20 ` Thomas Gleixner
2018-09-28 20:45 ` Andi Kleen
2018-09-29 6:19 ` Thomas Gleixner
2018-10-01 6:25 ` Alexey Budankov
2018-09-28 15:12 ` Jann Horn
2018-09-28 22:02 ` Jann Horn
2018-10-01 6:27 ` Alexey Budankov
2018-09-28 16:41 ` Mark Rutland [this message]
2018-09-28 17:23 ` Andi Kleen
2018-09-28 17:40 ` Mark Rutland
2018-09-28 20:49 ` Andi Kleen
2018-09-28 20:54 ` Jann Horn
2018-09-28 20:59 ` Andi Kleen
2018-09-28 21:22 ` Jann Horn
2018-09-28 21:27 ` Andi Kleen
2018-10-01 6:25 ` Alexey Budankov
2018-10-01 16:11 ` Thomas Gleixner
2018-10-01 16:15 ` Jann Horn
2018-10-01 20:51 ` Alexey Budankov
2018-10-02 6:40 ` Thomas Gleixner
2018-10-02 11:44 ` Alexey Budankov
2018-10-03 17:01 ` Jann Horn
2018-10-04 17:11 ` Alexey Budankov
2018-09-29 6:30 ` Thomas Gleixner
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