kernel-hardening - Re: [RFC][PATCH 1/3] mm/debug-pagealloc.c: Split out page poisoning from debug page

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Message-ID: <CAHz2CGXuUHYHX7KhxGjYtWrKOoxK=2Rz2N-Q0CBR9UWtrYi2Jw@mail.gmail.com>
Date: Tue, 26 Jan 2016 14:26:24 +0800
From: Jianyu Zhan <nasa4836@...il.com>
To: Laura Abbott <labbott@...oraproject.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>, 
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Vlastimil Babka <vbabka@...e.cz>, 
	Michal Hocko <mhocko@...e.com>, "linux-mm@...ck.org" <linux-mm@...ck.org>, 
	LKML <linux-kernel@...r.kernel.org>, kernel-hardening@...ts.openwall.com, 
	Kees Cook <keescook@...omium.org>
Subject: Re: [RFC][PATCH 1/3] mm/debug-pagealloc.c: Split out page poisoning
 from debug page_alloc

On Tue, Jan 26, 2016 at 12:55 AM, Laura Abbott
<labbott@...oraproject.org> wrote:
> +static bool __page_poisoning_enabled __read_mostly;
> +static bool want_page_poisoning __read_mostly =
> +       !IS_ENABLED(CONFIG_ARCH_SUPPORTS_DEBUG_PAGEALLOC);
> +

I would say this patch is nice with regard to decoupling
CONFIG_DEBUG_PAGEALLOC and CONFIG_PAGE_POISONING.

But  since when we enable CONFIG_DEBUG_PAGEALLOC,
CONFIG_PAGE_POISONING will be selected.

So it would be better to make page_poison.c totally
CONFIG_DEBUG_PAGEALLOC agnostic,  in case we latter have
more PAGE_POISONING users(currently only DEBUG_PAGEALLOC ). How about like this:

+static bool want_page_poisoning __read_mostly =
+       !IS_ENABLED(CONFIG_PAGE_POISONING );

Or just let it default to 'true',  since we only compile this
page_poison.c when we enable CONFIG_PAGE_POISONING.

Thanks,
Jianyu Zhan

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