userfaultfd: wp: drop _PAGE_UFFD_WP properly when fork

UFFD_EVENT_FORK support for uffd-wp should be already there, except that
we should clean the uffd-wp bit if uffd fork event is not enabled.  Detect
that to avoid _PAGE_UFFD_WP being set even if the VMA is not being tracked
by VM_UFFD_WP.  Do this for both small PTEs and huge PMDs.

Signed-off-by: Peter Xu <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Reviewed-by: Jerome Glisse <[email protected]>
Reviewed-by: Mike Rapoport <[email protected]>
Cc: Andrea Arcangeli <[email protected]>
Cc: Bobby Powers <[email protected]>
Cc: Brian Geffon <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Denis Plotnikov <[email protected]>
Cc: "Dr . David Alan Gilbert" <[email protected]>
Cc: Hugh Dickins <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: "Kirill A . Shutemov" <[email protected]>
Cc: Martin Cracauer <[email protected]>
Cc: Marty McFadden <[email protected]>
Cc: Maya Gokhale <[email protected]>
Cc: Mel Gorman <[email protected]>
Cc: Mike Kravetz <[email protected]>
Cc: Pavel Emelyanov <[email protected]>
Cc: Rik van Riel <[email protected]>
Cc: Shaohua Li <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Linus Torvalds <[email protected]>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 425339491677730c17ad7b1d03d43e37a3494972..8164787cd51f29d568ad3202544b126dc8dbed07 100644 (file)
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1044,6 +1044,14 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
        ret = -EAGAIN;
        pmd = *src_pmd;
 
+       /*
+        * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA
+        * does not have the VM_UFFD_WP, which means that the uffd
+        * fork event is not enabled.
+        */
+       if (!(vma->vm_flags & VM_UFFD_WP))
+               pmd = pmd_clear_uffd_wp(pmd);
+
 #ifdef CONFIG_ARCH_ENABLE_THP_MIGRATION
        if (unlikely(is_swap_pmd(pmd))) {
                swp_entry_t entry = pmd_to_swp_entry(pmd);

diff --git a/mm/memory.c b/mm/memory.c
index f35821b43c1bc8016759852992de6811a6505ffd..f8b1969669b7bdf1bc5847fc6cfdc22b7f0da404 100644 (file)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -785,6 +785,14 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
                pte = pte_mkclean(pte);
        pte = pte_mkold(pte);
 
+       /*
+        * Make sure the _PAGE_UFFD_WP bit is cleared if the new VMA
+        * does not have the VM_UFFD_WP, which means that the uffd
+        * fork event is not enabled.
+        */
+       if (!(vm_flags & VM_UFFD_WP))
+               pte = pte_clear_uffd_wp(pte);
+
        page = vm_normal_page(vma, addr, pte);
        if (page) {
                get_page(page);