linux-kernel - Re: [PATCH 2/2] mm/page_alloc.c: add config option to sanitize freed pages

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Message-ID: <CALUN=qLNX-ybF3_WWYMLjF2iqduEk4f5P0rs_9oE8-0rrSePyg@mail.gmail.com>
Date:	Mon, 27 Apr 2015 23:27:31 +0200
From:	Anisse Astier <anisse@...ier.eu>
To:	PaX Team <pageexec@...email.hu>
Cc:	Andi Kleen <andi@...stfloor.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mel Gorman <mgorman@...e.de>,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	David Rientjes <rientjes@...gle.com>,
	Alan Cox <gnomes@...rguk.ukuu.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Brad Spengler <spender@...ecurity.net>,
	Kees Cook <keescook@...omium.org>, linux-mm@...ck.org,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm/page_alloc.c: add config option to sanitize freed pages

On Mon, Apr 27, 2015 at 11:25 AM, PaX Team <pageexec@...email.hu> wrote:
>
> the PaX SANITIZE feature does exactly this in mm/page_alloc.c:prep_new_page:
>
> #ifndef CONFIG_PAX_MEMORY_SANITIZE
>         if (gfp_flags & __GFP_ZERO)
>                 prep_zero_page(page, order, gfp_flags);
> #endif
>

Thanks, I'll do that in the next iteration.

>> you'd need to clear memory on boot for example.
>
> it happens automagically because on boot during the transition from the
> boot allocator to the buddy one each page gets freed which will then go
> through the page clearing path.

Interesting, I'll see how it works.

>
> however there's a known problem/conflict with HIBERNATION (see
> http://marc.info/?l=linux-pm&m=132871433416256&w=2) which i think would
> have to be resolved before upstream acceptance.

I don't use hibernation, but I'll see if I can create a swap partition
to test that.

Regards,

Anisse
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