From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1754278AbcIKDQM (ORCPT <rfc822;w@1wt.eu>);
        Sat, 10 Sep 2016 23:16:12 -0400
Received: from mx1.redhat.com ([209.132.183.28]:47158 "EHLO mx1.redhat.com"
        rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP
        id S1751629AbcIKDQL (ORCPT <rfc822;linux-kernel@vger.kernel.org>);
        Sat, 10 Sep 2016 23:16:11 -0400
Date: Sun, 11 Sep 2016 05:16:06 +0200
From: Jiri Olsa <jolsa@redhat.com>
To: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>, Jiri Olsa <jolsa@kernel.org>,
        Wang Nan <wangnan0@huawei.com>, Josh Poimboeuf <jpoimboe@redhat.com>,
        Kees Cook <keescook@chromium.org>, Namhyung Kim <namhyung@kernel.org>,
        Ingo Molnar <mingo@kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: perf test "object code reading" segfaulting via usercopy check
Message-ID: <20160911031606.GA2025@krava>
References: <20160909153626.GD32585@kernel.org>
 <20160909154125.GA11319@krava>
 <20160909154720.GF32585@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20160909154720.GF32585@kernel.org>
User-Agent: Mutt/1.7.0 (2016-08-17)
X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Sun, 11 Sep 2016 03:16:10 +0000 (UTC)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Fri, Sep 09, 2016 at 12:47:20PM -0300, Arnaldo Carvalho de Melo wrote:
> Em Fri, Sep 09, 2016 at 05:41:25PM +0200, Jiri Olsa escreveu:
> > On Fri, Sep 09, 2016 at 12:36:26PM -0300, Arnaldo Carvalho de Melo wrote:
> > > Hi Adrian,
> > > 
> > > 	I noticed that 'perf test "object code reading"' is segfaulting
> > > here:
> > > 
> > > [root@jouet linux]# perf test -F "object code reading"
> > > 21: Test object code reading :Segmentation fault
> > > [root@jouet linux]# 
> > > 
> > > dmesg output below, trying to figure this out...
> > 
> > heya,
> > it's the new hardened user copy check.. I sent patches for that:
> > 
> >   http://marc.info/?l=linux-kernel&m=147332143929289&w=2
> >   http://marc.info/?l=linux-kernel&m=147332145229291&w=2
> 
> Cool, but that is for the kernel, without thinking too much about it, is
> there a way to change that 'perf test' entry to avoid doing what
> triggers the segfault?
> 
> My first thought was that it was reading 4K all the way to the end,
> where it should instead read just what is remaining, but I haven't
> checked this theory at all.

it's actually reading within the bounds of kernel text that triggers
that, it's the new CONFIG_HARDENED_USERCOPY feature:
  f5509cc18daa mm: Hardened usercopy

check the change log, there's list of conditions and
one of them is:
  - object must not overlap with kernel text

jirka