+ mm-shmem-fix-missing-cache-flush-in-shmem_mfill_atomic_pte.patch added to -mm tree

+ mm-shmem-fix-missing-cache-flush-in-shmem_mfill_atomic_pte.patch added to -mm tree

[Andrew Morton]

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

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

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

userfaultfd calls shmem_mfill_atomic_pte() 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.  Insert flush_dcache_page() in non-zero-page case.  And replace
clear_highpage() with clear_user_highpage() which already considers the
cache maintenance.

Link: https://lkml.kernel.org/r/20220210123058.79206-6-songmuchun@bytedance.com
Fixes: 8d1039634206 ("userfaultfd: shmem: add shmem_mfill_zeropage_pte for userfaultfd support")
Fixes: 4c27fe4c4c84 ("userfaultfd: shmem: add shmem_mcopy_atomic_pte for userfaultfd support")
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Cc: Axel Rasmussen <axelrasmussen@google.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Fam Zheng <fam.zheng@bytedance.com>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Lars Persson <lars.persson@axis.com>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Peter Xu <peterx@redhat.com>
Cc: Xiongchun Duan <duanxiongchun@bytedance.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/mm/shmem.c~mm-shmem-fix-missing-cache-flush-in-shmem_mfill_atomic_pte
+++ a/mm/shmem.c
@@ -2357,8 +2357,10 @@ int shmem_mfill_atomic_pte(struct mm_str
 				/* don't free the page */
 				goto out_unacct_blocks;
 			}
+
+			flush_dcache_page(page);
 		} else {		/* ZEROPAGE */
-			clear_highpage(page);
+			clear_user_highpage(page, dst_addr);
 		}
 	} else {
 		page = *pagep;
_

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-shmem-fix-missing-cache-flush-in-shmem_mfill_atomic_pte.patch
mm-userfaultfd-fix-missing-cache-flush-in-mcopy_atomic_pte-and-__mcopy_atomic.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