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

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

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

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

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

The userfaultfd calls copy_huge_page_from_user() which does not do any
cache flushing for the target page.  Then the target page will be mapped
to the user space with a different address (user address), which might
have an alias issue with the kernel address used to copy the data from the
user to.  Fix this issue by flushing dcache in copy_huge_page_from_user().

Link: https://lkml.kernel.org/r/20220208073617.70342-4-songmuchun@bytedance.com
Fixes: fa4d75c1de13 ("userfaultfd: hugetlbfs: add copy_huge_page_from_user for hugetlb userfaultfd support")
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/memory.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/mm/memory.c~mm-hugetlb-fix-missing-cache-flush-in-copy_huge_page_from_user
+++ a/mm/memory.c
@@ -5499,6 +5499,8 @@ long copy_huge_page_from_user(struct pag
 		if (rc)
 			break;
 
+		flush_dcache_page(subpage);
+
 		cond_resched();
 	}
 	return ret_val;
_

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