linux-kernel - Re: [PATCH v3 2/4] PM / Hibernate: prepare for SANITIZE_FREED

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Date:	Sat, 9 May 2015 17:44:55 +0200
From:	Pavel Machek <pavel@....cz>
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>,
	PaX Team <pageexec@...email.hu>,
	Brad Spengler <spender@...ecurity.net>,
	Kees Cook <keescook@...omium.org>,
	Andi Kleen <andi@...stfloor.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, linux-mm@...ck.org,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 2/4] PM / Hibernate: prepare for SANITIZE_FREED_PAGES

Hi!

> SANITIZE_FREED_PAGES feature relies on having all pages going through
> the free_pages_prepare path in order to be cleared before being used. In
> the hibernate use case, pages will automagically appear in the system
> without being cleared.
> 
> This patch will make sure free pages are cleared on resume; when we'll
> enable SANITIZE_FREED_PAGES. We free the pages just after resume because
> we can't do it later: going through any device resume code might
> allocate some memory and invalidate the free pages bitmap.
> 
> Signed-off-by: Anisse Astier <anisse@...ier.eu>
> ---
>  kernel/power/hibernate.c |  7 ++++++-
>  kernel/power/power.h     |  4 ++++
>  kernel/power/snapshot.c  | 21 +++++++++++++++++++++
>  3 files changed, 31 insertions(+), 1 deletion(-)
> 
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 2329daa..3193b9a 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -305,9 +305,14 @@ static int create_image(int platform_mode)
>  			error);
>  	/* Restore control flow magically appears here */
>  	restore_processor_state();
> -	if (!in_suspend)
> +	if (!in_suspend) {
>  		events_check_enabled = false;
>  
> +#ifdef CONFIG_SANITIZE_FREED_PAGES
> +		clear_free_pages();
> +		printk(KERN_INFO "PM: free pages cleared after restore\n");
> +#endif
> +	}
>  	platform_leave(platform_mode);
>  
>   Power_up:

Can you move the ifdef and the printk into the clear_free_pages?

This is not performance critical in any way...

Otherwise it looks good to me... if the sanitization is considered
useful. Did it catch some bugs in the past?

Thanks,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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