Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Date:   Fri, 28 Sep 2018 10:23:40 -0700
From:   Andi Kleen <ak@linux.intel.com>
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        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>,
        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)
Message-ID: <20180928172340.GA32651@tassilo.jf.intel.com>
References: <20180919122751.12439-1-tvrtko.ursulin@linux.intel.com>
 <alpine.DEB.2.21.1809281151190.2004@nanos.tec.linutronix.de>
 <20180928164111.i6nba2j6mnegwslw@lakrids.cambridge.arm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20180928164111.i6nba2j6mnegwslw@lakrids.cambridge.arm.com>
User-Agent: Mutt/1.10.1 (2018-07-13)
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

> 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