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References: <1429909549-11726-1-git-send-email-anisse@astier.eu>
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From: Anisse Astier <anisse@astier.eu>
Date: Mon, 27 Apr 2015 23:27:31 +0200
Message-ID: <CALUN=qLNX-ybF3_WWYMLjF2iqduEk4f5P0rs_9oE8-0rrSePyg@mail.gmail.com>
Subject: Re: [PATCH 2/2] mm/page_alloc.c: add config option to sanitize freed pages
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To: PaX Team <pageexec@freemail.hu>
Cc: Andi Kleen <andi@firstfloor.org>, Andrew Morton <akpm@linux-foundation.org>, Mel Gorman <mgorman@suse.de>, "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>, David Rientjes <rientjes@google.com>, Alan Cox <gnomes@lxorguk.ukuu.org.uk>, Linus Torvalds <torvalds@linux-foundation.org>, Peter Zijlstra <peterz@infradead.org>, Brad Spengler <spender@grsecurity.net>, Kees Cook <keescook@chromium.org>, linux-mm@kvack.org, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>

On Mon, Apr 27, 2015 at 11:25 AM, PaX Team <pageexec@freemail.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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