linux-kernel - Re: [PATCH] mm/hugetlb: avoid corrupting page->mapping in hugetlb_mcopy_atomic

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Date:   Mon, 18 Jul 2022 11:07:21 -0700
From:   Axel Rasmussen <axelrasmussen@...gle.com>
To:     Miaohe Lin <linmiaohe@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Peter Xu <peterx@...hat.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Muchun Song <songmuchun@...edance.com>,
        Linux MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] mm/hugetlb: avoid corrupting page->mapping in hugetlb_mcopy_atomic_pte

On Sun, Jul 17, 2022 at 7:25 PM Miaohe Lin <linmiaohe@...wei.com> wrote:
>
> On 2022/7/17 7:06, Andrew Morton wrote:
> > On Thu, 14 Jul 2022 17:59:53 +0800 Miaohe Lin <linmiaohe@...wei.com> wrote:
> >
> >> On 2022/7/14 1:23, Andrew Morton wrote:
> >>> On Tue, 12 Jul 2022 21:05:42 +0800 Miaohe Lin <linmiaohe@...wei.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:?
>
> I tend to backport this fix. And I think the Fixes tag in this patch should be suitable,
> i.e. Fixes: f619147104c8 ("userfaultfd: add UFFDIO_CONTINUE ioctl").

Agreed, it is worth backporting.

>
> Thanks.
>
> > .
> >
>