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

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Date:	Mon, 2 May 2016 13:34:52 +0200
From:	Alexander Potapenko <glider@...gle.com>
To:	Chen Gang <chengang@...ndsoft.com.cn>
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 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.

> So need use "!!kasan_depth" instead of "!kasan_depth" for checking
> enable.
>
> Signed-off-by: Chen Gang <gang.chen.5i5j@...il.com>
> ---
>  mm/kasan/kasan.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/mm/kasan/kasan.h b/mm/kasan/kasan.h
> index 7da78a6..6464b8f 100644
> --- a/mm/kasan/kasan.h
> +++ b/mm/kasan/kasan.h
> @@ -102,7 +102,7 @@ static inline const void *kasan_shadow_to_mem(const void *shadow_addr)
>
>  static inline bool kasan_report_enabled(void)
>  {
> -       return !current->kasan_depth;
> +       return !!current->kasan_depth;
>  }
>
>  void kasan_report(unsigned long addr, size_t size,
> --
> 1.9.3
>



-- 
Alexander Potapenko
Software Engineer

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