linux-kernel - Re: [PATCH] mm/kasan/kasan.h: Fix boolean checking issue for kasan_report

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Message-ID: <5727438A.1040409@emindsoft.com.cn>
Date:	Mon, 02 May 2016 20:09:46 +0800
From:	Chen Gang <chengang@...ndsoft.com.cn>
To:	Alexander Potapenko <glider@...gle.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Andrey Ryabinin <aryabinin@...tuozzo.com>,
	Dmitriy Vyukov <dvyukov@...gle.com>,
	kasan-dev <kasan-dev@...glegroups.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux Memory Management List <linux-mm@...ck.org>,
	Chen Gang <gang.chen.5i5j@...il.com>
Subject: Re: [PATCH] mm/kasan/kasan.h: Fix boolean checking issue for kasan_report_enabled()

On 5/2/16 19:34, Alexander Potapenko wrote:
> On Mon, May 2, 2016 at 7:36 AM,  <chengang@...ndsoft.com.cn> wrote:
>> From: Chen Gang <chengang@...ndsoft.com.cn>
>>
>> According to kasan_[dis|en]able_current() comments and the kasan_depth'
>> s initialization, if kasan_depth is zero, it means disable.
> The comments for those functions are really poor, but there's nothing
> there that says kasan_depth==0 disables KASAN.
> Actually, kasan_report_enabled() is currently the only place that
> denotes the semantics of kasan_depth, so it couldn't be wrong.
> 
> init_task.kasan_depth is 1 during bootstrap and is then set to zero by
> kasan_init()
> For every other thread, current->kasan_depth is zero-initialized.
> 

OK, what you said sound reasonable to me. and do you also mean:

 - kasan_depth == 0 means enable KASAN, others means disable KASAN.

 - If always let kasan_[en|dis]able_current() be pair, and notice about
   the overflow, it should be OK: "kasan_enable_current() can let
   kasan_depth++, and kasan_disable_current() will let kasan_depth--".

 - If we check the related overflow, "kasan_depth == 1" mean "the KASAN
   should be always in disable state".


Thanks.
-- 
Chen Gang (陈刚)

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