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Date:   Sat, 16 Jul 2022 16:06:29 -0700
From:   Andrew Morton <akpm@linux-foundation.org>
To:     Miaohe Lin <linmiaohe@huawei.com>
Cc:     <mike.kravetz@oracle.com>, <songmuchun@bytedance.com>,
        <linux-mm@kvack.org>, <linux-kernel@vger.kernel.org>,
        Axel Rasmussen <axelrasmussen@google.com>,
        Peter Xu <peterx@redhat.com>
Subject: Re: [PATCH] mm/hugetlb: avoid corrupting page->mapping in
 hugetlb_mcopy_atomic_pte
Message-Id: <20220716160629.d065828c84ad2423c10f7733@linux-foundation.org>
In-Reply-To: <a47922cf-eb30-1ad9-fc96-1896254564ef@huawei.com>
References: <20220712130542.18836-1-linmiaohe@huawei.com>
        <20220713102357.8328614813db01b569650ffd@linux-foundation.org>
        <a47922cf-eb30-1ad9-fc96-1896254564ef@huawei.com>
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On Thu, 14 Jul 2022 17:59:53 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:

> On 2022/7/14 1:23, Andrew Morton wrote:
> > On Tue, 12 Jul 2022 21:05:42 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:
> > 
> >> In MCOPY_ATOMIC_CONTINUE case with a non-shared VMA, pages in the page
> >> cache are installed in the ptes. But hugepage_add_new_anon_rmap is called
> >> for them mistakenly because they're not vm_shared. This will corrupt the
> >> page->mapping used by page cache code.
> > 
> > Well that sounds bad.  And theories on why this has gone unnoticed for
> > over a year?  I assume this doesn't have coverage in our selftests?
> 
> As discussed in another thread, when minor fault handling is proposed, only
> VM_SHARED vma is expected to be supported

So...  do we feel that this fix should be backported?  And if so, is
there a suitable commit for the Fixes:?