linux-kernel - Re: [PATCH] hwpoison: Fix race with changing page during offlining v2

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 1 Jul 2014 15:27:16 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>,
	Naoya Horiguchi <n-horiguchi@...jp.nec.com>
Subject: Re: [PATCH] hwpoison: Fix race with changing page during offlining
 v2

On Mon, 30 Jun 2014 17:32:16 -0700 Andi Kleen <andi@...stfloor.org> wrote:

> From: Andi Kleen <ak@...ux.intel.com>
> 
> When a hwpoison page is locked it could change state
> due to parallel modifications.  Check after the lock
> if the page is still the same compound page.
> 
> ...
>
> --- a/mm/memory-failure.c
> +++ b/mm/memory-failure.c
> @@ -1168,6 +1168,16 @@ int memory_failure(unsigned long pfn, int trapno, int flags)
>  	lock_page(hpage);
>  
>  	/*
> +	 * The page could have changed compound pages during the locking.
> +	 * If this happens just bail out.
> +	 */
> +	if (compound_head(p) != hpage) {

How can a 4k page change compound pages?  The original compound page
was torn down and then this 4k page became part of a differently-sized
compound page?

> +		action_result(pfn, "different compound page after locking", IGNORED);
> +		res = -EBUSY;
> +		goto out;
> +	}
> +
> +	/*

I don't get it.  We just go and fail the poisoning attempt?  Shouldn't
we go back, grab the new hpage and try again?


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/