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 <20220126060514.1574935-5-pasha.tatashin@soleen.com> <61833f93-31b5-206f-b8c7-a2e55091ac@google.com>
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From:   Pasha Tatashin <pasha.tatashin@soleen.com>
Date:   Wed, 26 Jan 2022 07:46:09 -0500
Message-ID: <CA+CK2bCd6OXW+PEB6NYvAN61xaaPzT5dWr=REidWX1=e1jrNCg@mail.gmail.com>
Subject: Re: [PATCH v3 4/4] mm/page_table_check: check entries at pmd levels
To:     David Rientjes <rientjes@google.com>
Cc:     LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Paul Turner <pjt@google.com>, Wei Xu <weixugc@google.com>,
        Greg Thelen <gthelen@google.com>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
        Mike Rapoport <rppt@kernel.org>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        "H. Peter Anvin" <hpa@zytor.com>,
        "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
        Jiri Slaby <jirislaby@kernel.org>,
        Muchun Song <songmuchun@bytedance.com>,
        Fusion Future <qydwhotmail@gmail.com>,
        Hugh Dickins <hughd@google.com>, Zi Yan <ziy@nvidia.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>
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On Wed, Jan 26, 2022 at 1:45 AM David Rientjes <rientjes@google.com> wrote:
>
> On Wed, 26 Jan 2022, Pasha Tatashin wrote:
>
> > syzbot detected a case where the page table counters were not properly
> > updated.
> >
>
> Is there a Reported-by tag that syzbot wants us to use to track this?

Google internal syzbot found it, so I did not add Reported-by as there
is no  public e-mail to reference. However, I added all the necessary
steps to repro this problem to the cover letter.

>
>
> This looks right, I'm wondering if we want to add a
> mmap_assert_write_locked(mm) to collapse_and_free_pmd().

Good idea, I will add it in the next revision.

Thanks,
Pasha