From: David Rientjes <rientjes@google.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Holger Kiehl <Holger.Kiehl@dwd.de>,
Christoph Lameter <cl@linux.com>,
Rafael Aquini <aquini@redhat.com>,
Vlastimil Babka <vbabka@suse.cz>, Michal Hocko <mhocko@suse.cz>,
Mel Gorman <mgorman@suse.de>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [patch] mm, page_alloc: make first_page visible before PageTail
Date: Tue, 4 Feb 2014 16:14:07 -0800 (PST) [thread overview]
Message-ID: <alpine.DEB.2.02.1402041613450.14962@chino.kir.corp.google.com> (raw)
In-Reply-To: <20140204160641.8f5d369eeb2d0318618d6d5f@linux-foundation.org>
On Tue, 4 Feb 2014, Andrew Morton wrote:
> > Commit bf6bddf1924e ("mm: introduce compaction and migration for ballooned
> > pages") introduces page_count(page) into memory compaction which
> > dereferences page->first_page if PageTail(page).
> >
> > Introduce a store memory barrier to ensure page->first_page is properly
> > initialized so that code that does page_count(page) on pages off the lru
> > always have a valid p->first_page.
>
> Could we have a code comment please? Even checkpatch knows this rule!
>
Ok.
> > Reported-by: Holger Kiehl <Holger.Kiehl@dwd.de>
>
> What did Holger report?
>
A once-in-five-years NULL pointer dereference on the aforementioned
page_count(page).
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next prev parent reply other threads:[~2014-02-05 0:14 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <alpine.LRH.2.02.1401312037340.6630@diagnostix.dwd.de>
2014-02-03 12:20 ` Need help in bug in isolate_migratepages_range Michal Hocko
2014-02-03 14:29 ` Holger Kiehl
2014-02-03 16:20 ` Michal Hocko
2014-02-03 16:52 ` Vlastimil Babka
2014-02-04 0:06 ` David Rientjes
2014-02-04 7:17 ` Holger Kiehl
2014-02-05 0:02 ` [patch] mm, page_alloc: make first_page visible before PageTail David Rientjes
2014-02-05 0:06 ` Andrew Morton
2014-02-05 0:14 ` David Rientjes [this message]
2014-02-05 0:22 ` [patch v2] " David Rientjes
2014-02-05 8:42 ` Michal Hocko
2014-02-12 9:00 ` [patch -mm] mm: close PageTail race David Rientjes
2014-02-03 19:50 ` Need help in bug in isolate_migratepages_range Holger Kiehl
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