linux-kernel - Re: [PATCH] arm64: disable kasan when accessing frame->fp in unwind

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Message-ID: <56B8CC75.1000508@linaro.org>
Date:	Mon, 8 Feb 2016 09:12:21 -0800
From:	"Shi, Yang" <yang.shi@...aro.org>
To:	Andrey Ryabinin <aryabinin@...tuozzo.com>, Will.Deacon@....com,
	Catalin.Marinas@....com
Cc:	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linaro-kernel@...ts.linaro.org
Subject: Re: [PATCH] arm64: disable kasan when accessing frame->fp in
 unwind_frame

On 2/8/2016 12:51 AM, Andrey Ryabinin wrote:
>
>
> On 02/06/2016 02:04 AM, Yang Shi wrote:
>>
>>   #include <asm/irq.h>
>>   #include <asm/stacktrace.h>
>> @@ -64,7 +65,9 @@ int notrace unwind_frame(struct task_struct *tsk, struct stackframe *frame)
>>   		return -EINVAL;
>>
>>   	frame->sp = fp + 0x10;
>> +	kasan_disable_current();
>>   	frame->fp = *(unsigned long *)(fp);
>
> It would be better to use READ_ONCE_NOCHECK() here.
> See f7d27c35ddff7 ("x86/mm, kasan: Silence KASAN warnings in get_wchan()") which solves the same problem for x86.

Thanks for the suggestion, I'm going to try it soon.

>
>> +	kasan_enable_current();
>>   	frame->pc = *(unsigned long *)(fp + 8);
>
> Why you left frame->pc out of scope? This line could trigger kasan as well.

Actually, it was not reported as frequently as the first one. In my 
first a couple of boot test, it was not triggered before I came up with 
the patch. The first one is triggered every time.

It will be fixed in v2 too.

Thanks,
Yang

>
>>
>>   #ifdef CONFIG_FUNCTION_GRAPH_TRACER
>>