linux-kernel - Re: [RFC 0/5] perf: Per PMU access controls (paranoid setting)

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Date:   Fri, 28 Sep 2018 10:23:40 -0700
From:   Andi Kleen <ak@...ux.intel.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Tvrtko Ursulin <tursulin@...ulin.net>,
        LKML <linux-kernel@...r.kernel.org>,
        tvrtko.ursulin@...ux.intel.com,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Madhavan Srinivasan <maddy@...ux.vnet.ibm.com>,
        Alexey Budankov <alexey.budankov@...ux.intel.com>,
        Kees Cook <keescook@...omium.org>, Jann Horn <jannh@...gle.com>
Subject: Re: [RFC 0/5] perf: Per PMU access controls (paranoid setting)

> 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.

That sounds like an orthogonal feature. I don't think the original
patchkit would need to be hold up for this. It would be something
in addition.

BTW can't you already do that with the syscall filter? I assume
the Android sandboxes already use that. Just forbid perf_event_open
for the apps.

-Andi