linux-kernel - Re: [PATCH 0/6] mempolicy memory corruption fixlet

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Message-ID: <CAHGf_=rS6cGjcJ7tKH05cMMdJKEO9f60mNBa0VaCkzs=kVjCQQ@mail.gmail.com>
Date:	Wed, 30 May 2012 16:00:55 -0400
From:	KOSAKI Motohiro <kosaki.motohiro@...il.com>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	Andrew Morton <akpm@...gle.com>, Dave Jones <davej@...hat.com>,
	Mel Gorman <mgorman@...e.de>, stable@...r.kernel.org,
	hughd@...gle.com, sivanich@....com
Subject: Re: [PATCH 0/6] mempolicy memory corruption fixlet

On Wed, May 30, 2012 at 3:52 PM, Andi Kleen <andi@...stfloor.org> wrote:
> On Wed, May 30, 2012 at 02:42:42PM -0500, Christoph Lameter wrote:
>> On Wed, 30 May 2012, Andi Kleen wrote:
>>
>> > On Wed, May 30, 2012 at 01:50:02PM -0500, Christoph Lameter wrote:
>> > > On Wed, 30 May 2012, Andi Kleen wrote:
>> > >
>> > > > I always regretted that cpusets were no done with custom node lists.
>> > > > That would have been much cleaner and also likely faster than what we have.
>> > >
>> > > Could shared memory policies ignore cpuset constraints?
>> >
>> > Only if noone uses cpusets as a "security" mechanism, just for a "soft policy"
>> > Even with soft policy you could well break someone's setup.
>>
>> Well at least lets exempt shared memory from memory migration and memory
>> policy updates. That seems to be causing many of these issues.
>
> Migration on the page level is needed for the memory error handling.
>
> Updates: you mean not allowing to set the policy when there are already
> multiple mappers? I could see that causing some unexpected behaviour. Presumably
> a standard database will only set it at the beginning, but I don't know
> if that would work for all users.

We don't need to kill migration core. We only need to kill that mbind(2) updates
vma->policy of shmem.

page migration for hwpoison is harmless. Because of, an attacker can't
inject hwpoison
intentntionally on production environment (HWPOISON_INJECTION=N).
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