From: Andrea Reale <ar@linux.vnet.ibm.com>
To: Zi Yan <zi.yan@cs.rutgers.edu>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Naoya Horiguchi" <n-horiguchi@ah.jp.nec.com>,
"Jérôme Glisse" <jglisse@redhat.com>,
stable@vger.kernel.org
Subject: Re: [PATCH] mm: migrate: fix an incorrect call of prep_transhuge_page()
Date: Wed, 22 Nov 2017 09:43:34 +0000 [thread overview]
Message-ID: <20171122094333.GA24826@samekh> (raw)
In-Reply-To: <73A54AD9-33E0-4C82-8C9F-6E1786ED6132@cs.rutgers.edu>
On Tue 21 Nov 2017, 17:35, Zi Yan wrote:
> On 21 Nov 2017, at 17:12, Andrew Morton wrote:
>
> > On Mon, 20 Nov 2017 21:18:55 -0500 Zi Yan <zi.yan@sent.com> wrote:
> >
> >> This patch fixes it by only calling prep_transhuge_page() when we are
> >> certain that the target page is THP.
> >
> > What are the user-visible effects of the bug?
>
> By inspecting the code, if called on a non-THP, prep_transhuge_page() will
> 1) change the value of the mapping of (page + 2), since it is used for THP deferred list;
> 2) change the lru value of (page + 1), since it is used for THPa??s dtor.
>
> Both can lead to data corruption of these two pages.
Pragmatically and from the point of view of the memory_hotplug subsys,
the effect is a kernel crash when pages are being migrated during a memory
hot remove offline and migration target pages are found in a bad state.
Best,
Andrea
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next prev parent reply other threads:[~2017-11-22 9:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-21 2:18 [PATCH] mm: migrate: fix an incorrect call of prep_transhuge_page() Zi Yan
2017-11-21 22:12 ` Andrew Morton
2017-11-21 22:35 ` Zi Yan
2017-11-22 9:43 ` Andrea Reale [this message]
2017-11-22 8:54 ` Michal Hocko
2017-11-22 9:18 ` Zi Yan
2017-11-22 9:35 ` Michal Hocko
2017-11-22 10:14 ` Michal Hocko
2017-11-22 12:13 ` Zi Yan
2017-11-22 12:29 ` Zi Yan
2017-11-22 13:01 ` Michal Hocko
2017-11-22 13:40 ` Michal Hocko
2017-11-22 14:43 ` Zi Yan
2017-11-22 14:53 ` Michal Hocko
2017-11-22 15:09 ` Zi Yan
2017-11-22 15:39 ` Michal Hocko
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