Messages in this thread | | | Date | Wed, 2 Nov 2022 13:47:14 -0700 | From | Andrew Morton <> | Subject | Re: [PATCH 3/5] userfualtfd: Replace lru_cache functions with folio_add functions |
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On Wed, 2 Nov 2022 15:02:35 -0400 Peter Xu <peterx@redhat.com> wrote:
> mfill_atomic_install_pte() checks page->mapping to detect whether one page > is used in the page cache. However as pointed out by Matthew, the page can > logically be a tail page rather than always the head in the case of uffd > minor mode with UFFDIO_CONTINUE. It means we could wrongly install one pte > with shmem thp tail page assuming it's an anonymous page. > > It's not that clear even for anonymous page, since normally anonymous pages > also have page->mapping being setup with the anon vma. It's safe here only > because the only such caller to mfill_atomic_install_pte() is always > passing in a newly allocated page (mcopy_atomic_pte()), whose page->mapping > is not yet setup. However that's not extremely obvious either. > > For either of above, use page_mapping() instead. > > And this should be stable material.
I added
Fixes: 153132571f02 ("userfaultfd/shmem: support UFFDIO_CONTINUE for shmem")
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