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Date: Fri, 19 May 2017 19:40:38 -0700 (PDT)
From: Hugh Dickins <hughd@google.com>
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To: Xishi Qiu <qiuxishi@huawei.com>
cc: Hugh Dickins <hughd@google.com>,
        Andrew Morton <akpm@linux-foundation.org>, Tejun Heo <tj@kernel.org>,
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        Minchan Kim <minchan@kernel.org>, David Rientjes <rientjes@google.com>,
        Joonsoo Kim <iamjoonsoo.kim@lge.com>, aarcange@redhat.com,
        sumeet.keswani@hpe.com, Rik van Riel <riel@redhat.com>,
        Linux MM <linux-mm@kvack.org>, LKML <linux-kernel@vger.kernel.org>,
        zhong jiang <zhongjiang@huawei.com>
Subject: Re: mm, something wring in page_lock_anon_vma_read()?
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On Sat, 20 May 2017, Xishi Qiu wrote:
> 
> Here is a bug report form redhat: https://bugzilla.redhat.com/show_bug.cgi?id=1305620
> And I meet the bug too. However it is hard to reproduce, and 
> 624483f3ea82598("mm: rmap: fix use-after-free in __put_anon_vma") is not help.
> 
> From the vmcore, it seems that the page is still mapped(_mapcount=0 and _count=2),
> and the value of mapping is a valid address(mapping = 0xffff8801b3e2a101),
> but anon_vma has been corrupted.
> 
> Any ideas?

Sorry, no.  I assume that _mapcount has been misaccounted, for example
a pte mapped in on top of another pte; but cannot begin tell you where
in Red Hat's kernel-3.10.0-229.4.2.el7 that might happen.

Hugh