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

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Message-ID: <CALUN=q+OZFarqRoWMynRZy0ckv7qnsAQvWr9wkvdK_JmA=oomw@mail.gmail.com>
Date:	Mon, 11 May 2015 09:59:23 +0200
From:	Anisse Astier <anisse@...ier.eu>
To:	Pavel Machek <pavel@....cz>
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 list <linux-pm@...r.kernel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 2/4] PM / Hibernate: prepare for SANITIZE_FREED_PAGES

Hi Pavel,

Thanks a lot for taking the time to review this.

On Sat, May 9, 2015 at 5:44 PM, Pavel Machek <pavel@....cz> wrote:
>> +#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?

Sure. I put the printk out originally because i thought there might be
other uses, but since this is the sole call site right now it
shouldn't be an issue.

>
> 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?
>

I've read somewhere that users of grsecurity claim that it caught bugs
in some drivers, but I haven't verified that personally; it's probably
much less useful than kasan (or even the original grsec feature) as a
bug-catcher since it doesn't clear freed slab buffers.

I'll wait a few more days for more reviews before sending the next
version, particularly on the power management part, and in general on
the usefulness of such feature.

Regards,

Anisse
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