linux-kernel - Re: [PATCH v2 2/4] mm/page_alloc.c: add config option to sanitize freed pages

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Date:	Mon, 04 May 2015 23:50:14 +0200
From:	"PaX Team" <pageexec@...email.hu>
To:	Anisse Astier <anisse@...ier.eu>
CC:	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>,
	Andi Kleen <andi@...stfloor.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/4] mm/page_alloc.c: add config option to sanitize freed pages

On 4 May 2015 at 23:16, Anisse Astier wrote:

> @@ -960,9 +966,15 @@ static int prep_new_page(struct page *page, unsigned int order, gfp_t gfp_flags,
>  	kernel_map_pages(page, 1 << order, 1);
>  	kasan_alloc_pages(page, order);
>  
> +#ifndef CONFIG_SANITIZE_FREED_PAGES
> +	/* SANITIZE_FREED_PAGES relies implicitly on the fact that pages are
> +	 * cleared before use, so we don't need gfp zero in the default case
> +	 * because all pages go through the free_pages_prepare code path when
> +	 * switching from bootmem to the default allocator */
>  	if (gfp_flags & __GFP_ZERO)
>  		for (i = 0; i < (1 << order); i++)
>  			clear_highpage(page + i);
> +#endif

this hunk should not be applied before the hibernation fix otherwise
bisect will break.

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