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 S1756706AbcBINjN (ORCPT <rfc822;w@1wt.eu>);
	Tue, 9 Feb 2016 08:39:13 -0500
Received: from mx2.parallels.com ([199.115.105.18]:35109 "EHLO
	mx2.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1756051AbcBINjM (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Tue, 9 Feb 2016 08:39:12 -0500
Subject: Re: [PATCH] trace, kasan: silence Kasan warning in check_stack
To: Yang Shi <yang.shi@linaro.org>, <rostedt@goodmis.org>, <mingo@redhat.com>
References: <1454956782-5944-1-git-send-email-yang.shi@linaro.org>
CC: <linux-kernel@vger.kernel.org>, <linaro-kernel@lists.linaro.org>
From: Andrey Ryabinin <aryabinin@virtuozzo.com>
Message-ID: <56B9EC3C.4040405@virtuozzo.com>
Date: Tue, 9 Feb 2016 16:40:12 +0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101
 Thunderbird/38.5.0
MIME-Version: 1.0
In-Reply-To: <1454956782-5944-1-git-send-email-yang.shi@linaro.org>
Content-Type: text/plain; charset="windows-1252"
Content-Transfer-Encoding: 7bit
X-ClientProxiedBy: US-EXCH.sw.swsoft.com (10.255.249.47) To
 US-EXCH.sw.swsoft.com (10.255.249.47)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 02/08/2016 09:39 PM, Yang Shi wrote:
> When enabling stack trace via "echo 1 > /proc/sys/kernel/stack_tracer_enabled",
> the below KASAN warning is triggered:
> 
> BUG: KASAN: stack-out-of-bounds in check_stack+0x344/0x848 at addr ffffffc0689ebab8
> Read of size 8 by task ksoftirqd/4/29
> page:ffffffbdc3a27ac0 count:0 mapcount:0 mapping:          (null) index:0x0
> flags: 0x0()
> page dumped because: kasan: bad access detected
> CPU: 4 PID: 29 Comm: ksoftirqd/4 Not tainted 4.5.0-rc1 #129
> Hardware name: Freescale Layerscape 2085a RDB Board (DT)
> Call trace:
> [<ffffffc000091300>] dump_backtrace+0x0/0x3a0
> [<ffffffc0000916c4>] show_stack+0x24/0x30
> [<ffffffc0009bbd78>] dump_stack+0xd8/0x168
> [<ffffffc000420bb0>] kasan_report_error+0x6a0/0x920
> [<ffffffc000421688>] kasan_report+0x70/0xb8
> [<ffffffc00041f7f0>] __asan_load8+0x60/0x78
> [<ffffffc0002e05c4>] check_stack+0x344/0x848
> [<ffffffc0002e0c8c>] stack_trace_call+0x1c4/0x370
> [<ffffffc0002af558>] ftrace_ops_no_ops+0x2c0/0x590
> [<ffffffc00009f25c>] ftrace_graph_call+0x0/0x14
> [<ffffffc0000881bc>] fpsimd_thread_switch+0x24/0x1e8
> [<ffffffc000089864>] __switch_to+0x34/0x218
> [<ffffffc0011e089c>] __schedule+0x3ac/0x15b8
> [<ffffffc0011e1f6c>] schedule+0x5c/0x178
> [<ffffffc0001632a8>] smpboot_thread_fn+0x350/0x960
> [<ffffffc00015b518>] kthread+0x1d8/0x2b0
> [<ffffffc0000874d0>] ret_from_fork+0x10/0x40
> Memory state around the buggy address:
>  ffffffc0689eb980: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 f4 f4 f4
>  ffffffc0689eba00: f3 f3 f3 f3 00 00 00 00 00 00 00 00 00 00 00 00
>> ffffffc0689eba80: 00 00 f1 f1 f1 f1 00 f4 f4 f4 f3 f3 f3 f3 00 00
>                                         ^
>  ffffffc0689ebb00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffffffc0689ebb80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> 
> The stacker tracer traverses the whole kernel stack when saving the max stack
> trace. It may touch the stack red zones to cause the warning. So, just disable
> the instrumentation to silence the warning.
> 
> Signed-off-by: Yang Shi <yang.shi@linaro.org>

Acked-by: Andrey Ryabinin <aryabinin@virtuozzo.com>