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 S1754181AbcDKJdd (ORCPT <rfc822;w@1wt.eu>);
	Mon, 11 Apr 2016 05:33:33 -0400
Received: from mail-lf0-f45.google.com ([209.85.215.45]:36304 "EHLO
	mail-lf0-f45.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1754039AbcDKJcL (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 11 Apr 2016 05:32:11 -0400
Subject: Re: x86: bad pte in pageattr_test
To: Dmitry Vyukov <dvyukov@google.com>
References: <CACT4Y+YwV++Eb8n-1q94zW7_rOOX=p8_+8ERD9L07cjrBf7ysw@mail.gmail.com>
 <570B65DC.6090404@gmail.com>
 <CACT4Y+ZZ_SJ=qiqWLu4NgeOUdiQPH_YvWXS5cn03uLkFU9R8Lg@mail.gmail.com>
Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, "x86@kernel.org" <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        Konstantin Khlebnikov <koct9i@gmail.com>,
        syzkaller <syzkaller@googlegroups.com>,
        Kostya Serebryany <kcc@google.com>,
        Alexander Potapenko <glider@google.com>,
        Sasha Levin <sasha.levin@oracle.com>
From: Andrey Ryabinin <ryabinin.a.a@gmail.com>
Message-ID: <570B6F2E.8070109@gmail.com>
Date: Mon, 11 Apr 2016 12:32:30 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.7.0
MIME-Version: 1.0
In-Reply-To: <CACT4Y+ZZ_SJ=qiqWLu4NgeOUdiQPH_YvWXS5cn03uLkFU9R8Lg@mail.gmail.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: 7bit
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org



On 04/11/2016 12:03 PM, Dmitry Vyukov wrote:
> On Mon, Apr 11, 2016 at 10:52 AM, Andrey Ryabinin
> <ryabinin.a.a@gmail.com> wrote:
>>
>>
>> On 04/11/2016 11:28 AM, Dmitry Vyukov wrote:
>>> Hello,
>>>
>>> I've got the following WARNING while running syzkaller fuzzer:
>>>
>>> CPA ffff880054118000: bad pte after revert 8000000054118363
>>> ------------[ cut here ]------------
>>> WARNING: CPU: 2 PID: 1503 at arch/x86/mm/pageattr-test.c:226
>>> pageattr_test+0xa6c/0xd10
>>> NOT PASSED. Please report.
>>> Modules linked in:
>>> CPU: 2 PID: 1503 Comm: pageattr-test Not tainted 4.6.0-rc2+ #346
>>> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
>>>  ffffffff87eb25c0 ffff88003b627a70 ffffffff82c8b17f ffffffff81490b58
>>>  fffffbfff0fd64b8 ffff88003b627ae8 0000000000000000 ffffffff86a77e00
>>>  ffffffff8129487c 0000000000000009 ffff88003b627ab8 ffffffff8136639f
>>> Call Trace:
>>>  [<     inline     >] __dump_stack lib/dump_stack.c:15
>>>  [<ffffffff82c8b17f>] dump_stack+0x12e/0x18f lib/dump_stack.c:51
>>>  [<ffffffff8136639f>] __warn+0x19f/0x1e0 kernel/panic.c:512
>>>  [<ffffffff8136648c>] warn_slowpath_fmt+0xac/0xd0 kernel/panic.c:527
>>>  [<ffffffff8129487c>] pageattr_test+0xa6c/0xd10 arch/x86/mm/pageattr-test.c:226
>>>  [<ffffffff81294b3b>] do_pageattr_test+0x1b/0x60 arch/x86/mm/pageattr-test.c:240
>>>  [<ffffffff813cde7f>] kthread+0x23f/0x2d0 drivers/block/aoe/aoecmd.c:1303
>>
>> It seems, that your script is buggy. It should be kthread() from kernel/kthread.c here.
> 
> 
> I probably used a non-matching vmlinux for symbolization. 

No, it's a bug in your script. To find out source location, it uses 'function_name + offset' instead of absolute address.
We have 2 kthread() functions in kernel and this confuses you script.


E.g. my vmlinux :
 $ addr2line -i -e vmlinux ffffffff811b5290
	/home/andrew/linux/kernel/kthread.c:178
 $ addr2line -i -e kasan_conf/vmlinux ffffffff825c7240
	/home/andrew/linux/drivers/block/aoe/aoecmd.c:1289


 $ echo '[<ffffffff811b5290>] kthread+0x00/0x00' | python kasan_symbolize.py vmlinux
	[<ffffffff811b5290>] kthread+0x00/0x00 drivers/block/aoe/aoecmd.c:462
 $ echo '[<ffffffff825c7240>] kthread+0x00/0x00' | python kasan_symbolize.py vmlinux
	[<ffffffff825c7240>] kthread+0x00/0x00 drivers/block/aoe/aoecmd.c:462

> Please
> check the raw report below if the symbolized one does not make sense.
> 
> \/\/\/\/\/\/\/\/
> 
>>> For the repcord, full syzkaller log:
>>> https://gist.githubusercontent.com/dvyukov/323ff7275c5ac38156cb40caeacac057/raw/0836f8dd81024e441f81caebdcb73ca1221aef97/gistfile1.txt