From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wm0-f71.google.com (mail-wm0-f71.google.com [74.125.82.71]) by kanga.kvack.org (Postfix) with ESMTP id 144826B0279 for ; Tue, 23 May 2017 05:33:30 -0400 (EDT) Received: by mail-wm0-f71.google.com with SMTP id b20so28332447wma.11 for ; Tue, 23 May 2017 02:33:30 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id n6si14948107wra.196.2017.05.23.02.33.28 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 23 May 2017 02:33:28 -0700 (PDT) Subject: Re: mm, something wring in page_lock_anon_vma_read()? References: <591D6D79.7030704@huawei.com> <591EB25C.9080901@huawei.com> <591EBE71.7080402@huawei.com> <591F9A09.6010707@huawei.com> <591FA78E.9050307@huawei.com> <591FB173.4020409@huawei.com> <5923FF31.5020801@huawei.com> From: Vlastimil Babka Message-ID: Date: Tue, 23 May 2017 11:33:23 +0200 MIME-Version: 1.0 In-Reply-To: <5923FF31.5020801@huawei.com> Content-Type: text/plain; charset=windows-1252 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: zhong jiang Cc: Hugh Dickins , Xishi Qiu , Andrew Morton , Tejun Heo , Michal Hocko , Johannes Weiner , Mel Gorman , Michal Hocko , Minchan Kim , David Rientjes , Joonsoo Kim , aarcange@redhat.com, sumeet.keswani@hpe.com, Rik van Riel , Linux MM , LKML On 05/23/2017 11:21 AM, zhong jiang wrote: > On 2017/5/23 0:51, Vlastimil Babka wrote: >> 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") > HI, Vlastimil > > I miss the patch. Try applying it then, there's good chance the error and crash will go away. Even if your workload doesn't actually run any madvise(MADV_DONTNEED). > when I read the patch. I find the following issue. but I am sure it is right. > > if (unlikely(pmd_trans_unstable(pmd))) > return 0; > /* > * A regular pmd is established and it can't morph into a huge pmd > * from under us anymore at this point because we hold the mmap_sem > * read mode and khugepaged takes it in write mode. So now it's > * safe to run pte_offset_map(). > */ > pte = pte_offset_map(pmd, address); > > after pmd_trans_unstable call, without any protect method. by the comments, > it think the pte_offset_map is safe. before pte_offset_map call, it still may be > unstable. it is possible? IIRC it's "unstable" wrt possible none->huge->none transition. But once we've seen it's a regular pmd via pmd_trans_unstable(), we're safe as a transition from regular pmd can't happen. > Thanks > zhongjiang >>> Thanks >>> zhongjiang >>> >>> -- >>> To unsubscribe, send a message with 'unsubscribe linux-mm' in >>> the body to majordomo@kvack.org. For more info on Linux MM, >>> see: http://www.linux-mm.org/ . >>> Don't email: email@kvack.org >>> >> >> . >> > > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to majordomo@kvack.org. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: email@kvack.org > -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org