+ mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte.patch added to -mm tree

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm: hugetlb: fix missing cache flush in hugetlb_mcopy_atomic_pte()
has been added to the -mm tree.  Its filename is
     mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte.patch

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------------------------------------------------------
From: Muchun Song <songmuchun@bytedance.com>
Subject: mm: hugetlb: fix missing cache flush in hugetlb_mcopy_atomic_pte()

folio_copy() will copy the data from one page to the target page, then the
target page will be mapped to the user space address, which might have an
alias issue with the kernel address used to copy the data from the page
to.  There are 2 ways to fix this issue.

 1) insert flush_dcache_page() after folio_copy().
 2) replace folio_copy() with copy_user_huge_page() which already
    considers the cache maintenance.

We chose 2) to fix the issue since architectures can optimize this
situation.

Link: https://lkml.kernel.org/r/20220208073617.70342-5-songmuchun@bytedance.com
Fixes: 8cc5fcbb5be8 ("mm, hugetlb: fix racy resv_huge_pages underflow on UFFDIO_COPY")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lars Persson <lars.persson@axis.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Mina Almasry <almasrymina@google.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/hugetlb.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/mm/hugetlb.c~mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte
+++ a/mm/hugetlb.c
@@ -5817,7 +5817,8 @@ int hugetlb_mcopy_atomic_pte(struct mm_s
 			*pagep = NULL;
 			goto out;
 		}
-		folio_copy(page_folio(page), page_folio(*pagep));
+		copy_user_huge_page(page, *pagep, dst_addr, dst_vma,
+				    pages_per_huge_page(h));
 		put_page(*pagep);
 		*pagep = NULL;
 	}
_

Patches currently in -mm which might be from songmuchun@bytedance.com are

mm-thp-fix-wrong-cache-flush-in-remove_migration_pmd.patch
mm-fix-missing-cache-flush-for-all-tail-pages-of-compound-page.patch
mm-hugetlb-fix-missing-cache-flush-in-copy_huge_page_from_user.patch
mm-hugetlb-fix-missing-cache-flush-in-hugetlb_mcopy_atomic_pte.patch
mm-replace-multiple-dcache-flush-with-flush_dcache_folio.patch
mm-hugetlb-free-the-2nd-vmemmap-page-associated-with-each-hugetlb-page.patch
mm-hugetlb-replace-hugetlb_free_vmemmap_enabled-with-a-static_key.patch
mm-sparsemem-use-page-table-lock-to-protect-kernel-pmd-operations.patch
selftests-vm-add-a-hugetlb-test-case.patch
mm-sparsemem-move-vmemmap-related-to-hugetlb-to-config_hugetlb_page_free_vmemmap.patch