linux-kernel - Re: mm, something wring in page_lock_anon_vma

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Date:   Mon, 22 May 2017 18:51:58 +0200
From:   Vlastimil Babka <vbabka@...e.cz>
To:     zhong jiang <zhongjiang@...wei.com>,
        Hugh Dickins <hughd@...gle.com>
Cc:     Xishi Qiu <qiuxishi@...wei.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Tejun Heo <tj@...nel.org>, Michal Hocko <mhocko@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Hocko <mhocko@...e.com>,
        Minchan Kim <minchan@...nel.org>,
        David Rientjes <rientjes@...gle.com>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, aarcange@...hat.com,
        sumeet.keswani@....com, Rik van Riel <riel@...hat.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: mm, something wring in page_lock_anon_vma_read()?

On 05/20/2017 05:01 AM, zhong jiang wrote:
> On 2017/5/20 10:40, Hugh Dickins wrote:
>> 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
>>
>> .
>>
> Hi, Hugh
> 
> I find the following message from the dmesg.
> 
> [26068.316592] BUG: Bad rss-counter state mm:ffff8800a7de2d80 idx:1 val:1
> 
> I can prove that the __mapcount is misaccount.  when task is exited. the rmap
> still exist.

Check if the kernel in question contains this commit: ad33bb04b2a6 ("mm:
thp: fix SMP race condition between THP page fault and MADV_DONTNEED")

> Thanks
> zhongjiang
> 
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