linux-kernel - Re: [PATCH] trace, kasan: silence Kasan warning in check

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Date:	Fri, 12 Feb 2016 10:50:36 -0800
From:	"Shi, Yang" <yang.shi@...aro.org>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>, rostedt@...dmis.org,
	mingo@...hat.com
Cc:	linux-kernel@...r.kernel.org, linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] trace, kasan: silence Kasan warning in check_stack

Hi Steven,

Any comment for this patch?

Thanks,
Yang


On 2/9/2016 5:40 AM, Andrey Ryabinin wrote:
> 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@...aro.org>
>
> Acked-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
>