Commit 7d049f3a authored by Peter Xu's avatar Peter Xu Committed by Andrew Morton
Browse files

mm/hugetlb: make hugetlb_follow_page_mask() safe to pmd unshare 

Since hugetlb_follow_page_mask() walks the pgtable, it needs the vma lock
to make sure the pgtable page will not be freed concurrently.

Link: https://lkml.kernel.org/r/20221216155219.2043714-1-peterx@redhat.com


Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Acked-by: default avatarDavid Hildenbrand <david@redhat.com>
Reviewed-by: default avatarMike Kravetz <mike.kravetz@oracle.com>
Reviewed-by: default avatarJohn Hubbard <jhubbard@nvidia.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: James Houghton <jthoughton@google.com>
Cc: Jann Horn <jannh@google.com>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Muchun Song <songmuchun@bytedance.com>
Cc: Nadav Amit <nadav.amit@gmail.com>
Cc: Rik van Riel <riel@surriel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent b8da2e46

mm/hugetlb.c

+4 −1
Original line number Diff line number Diff line
@@ -6396,9 +6396,10 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, 
	if (WARN_ON_ONCE(flags & FOLL_PIN))

		return NULL;



	hugetlb_vma_lock_read(vma);

	pte = huge_pte_offset(mm, haddr, huge_page_size(h));

	if (!pte)

		return NULL;

		goto out_unlock;



	ptl = huge_pte_lock(h, mm, pte);

	entry = huge_ptep_get(pte);
@@ -6421,6 +6422,8 @@ struct page *hugetlb_follow_page_mask(struct vm_area_struct *vma, 
	}

out:

	spin_unlock(ptl);

out_unlock:

	hugetlb_vma_unlock_read(vma);

	return page;

}