On 14.04.23 01:11, Peter Xu wrote:
When we try to unshare a pinned page for a private hugetlb, uffd-wp bit can get lost during unsharing. Fix it by carrying it over.
This should be very rare, only if an unsharing happened on a private hugetlb page with uffd-wp protected (e.g. in a child which shares the same page with parent with UFFD_FEATURE_EVENT_FORK enabled).
Cc: linux-stable stable@vger.kernel.org Fixes: 166f3ecc0daf ("mm/hugetlb: hook page faults for uffd write protection") Reported-by: Mike Kravetz mike.kravetz@oracle.com Signed-off-by: Peter Xu peterx@redhat.com
mm/hugetlb.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-)
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 7320e64aacc6..083aae35bff8 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -5637,13 +5637,16 @@ static vm_fault_t hugetlb_wp(struct mm_struct *mm, struct vm_area_struct *vma, spin_lock(ptl); ptep = hugetlb_walk(vma, haddr, huge_page_size(h)); if (likely(ptep && pte_same(huge_ptep_get(ptep), pte))) {
pte_t newpte = make_huge_pte(vma, &new_folio->page, !unshare);- /* Break COW or unshare */ huge_ptep_clear_flush(vma, haddr, ptep); mmu_notifier_invalidate_range(mm, range.start, range.end); page_remove_rmap(old_page, vma, true); hugepage_add_new_anon_rmap(new_folio, vma, haddr);
set_huge_pte_at(mm, haddr, ptep,make_huge_pte(vma, &new_folio->page, !unshare));
if (huge_pte_uffd_wp(pte))newpte = huge_pte_mkuffd_wp(newpte);set_huge_pte_at(mm, haddr, ptep, newpte);
LGTM, thanks
Reviewed-by: David Hildenbrand david@redhat.com