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 <peterx@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Reviewed-by: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Bobby Powers <bobbypowers@gmail.com>
Cc: Brian Geffon <bgeffon@google.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Denis Plotnikov <dplotnikov@virtuozzo.com>
Cc: "Dr . David Alan Gilbert" <dgilbert@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Martin Cracauer <cracauer@cons.org>
Cc: Marty McFadden <mcfadden8@llnl.gov>
Cc: Maya Gokhale <gokhale2@llnl.gov>
Cc: Mel Gorman <mgorman@suse.de>
Cc: Mike Kravetz <mike.kravetz@oracle.com>
Cc: Pavel Emelyanov <xemul@openvz.org>
Cc: Rik van Riel <riel@redhat.com>
Cc: Shaohua Li <shli@fb.com>
Link: http://lkml.kernel.org/r/20200220163112.11409-9-peterx@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 4253394..8164787 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 f35821b..f8b1969 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);