linux-kernel - Re: [kernel-hardening] [PATCH 1/2] security, perf: allow further restriction of perf_event

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Message-ID: <20161019102602.GA25522@kernel.org>
Date:   Wed, 19 Oct 2016 07:26:02 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Daniel Micay <danielmicay@...il.com>,
        kernel-hardening@...ts.openwall.com,
        Mark Rutland <mark.rutland@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jeff Vander Stoep <jeffv@...gle.com>
Subject: Re: [kernel-hardening] [PATCH 1/2] security, perf: allow further
 restriction of perf_event_open

Em Wed, Oct 19, 2016 at 12:01:26PM +0200, Peter Zijlstra escreveu:
> On Tue, Oct 18, 2016 at 05:15:01PM -0400, Daniel Micay wrote:
> > It's also worth noting that fine-grained control via a scoped mechanism
> > would likely only be used to implement *more restrictions* on Android,
> > not to make the feature less aggressive.
 
> > It's desirable for perf events to be disabled by default for non-root
> > across the board on Android.
 
> Right, but this is Android. The knob seems to now also live in Debian
> (and derived) distros. And there it is utter crap.
 
> It completely defeats having perf for a fairly large segment of
> corporate developers who do not get to have root on their own machines
> (which is stupid policy but whatever).
 
> It similarly defeats development of self profiling JITs and whatnot.
 
> A capability would allow people to run perf (or another sanctioned
> binary), even though in general they cannot do sys_perf_event_open().

But self profiling JITs would be useful for non-developers, on Android
(anywhere, really), and for that it would require being able to at
least, well, self profile, using sys_perf_event_open() by a normal
process, limited to profiling itself, no?

This not being possible, self profiling will use some other means, its
like sys_perf_event_open() never existed for them.

- Arnaldo