move_present_ptes() unconditionally makes the destination PTE writable, dropping uffd-wp write-protection from the source PTE. The original intent was to follow mremap() behavior, but mremap()'s move_ptes() preserves the source write state unconditionally. Modify uffd to preserve the source write state and check the uffd-wp condition of the source before setting writable on the destination. Fixes: adef440691ba ("userfaultfd: UFFDIO_MOVE uABI") Cc: stable@vger.kernel.org Signed-off-by: Gregory Price --- mm/userfaultfd.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c index e6dfd5f28acd..783ca68aed88 100644 --- a/mm/userfaultfd.c +++ b/mm/userfaultfd.c @@ -1123,7 +1123,10 @@ static long move_present_ptes(struct mm_struct *mm, orig_dst_pte = pte_mksoft_dirty(orig_dst_pte); if (pte_dirty(orig_src_pte)) orig_dst_pte = pte_mkdirty(orig_dst_pte); - orig_dst_pte = pte_mkwrite(orig_dst_pte, dst_vma); + if (pte_write(orig_src_pte)) + orig_dst_pte = pte_mkwrite(orig_dst_pte, dst_vma); + if (pte_uffd_wp(orig_src_pte)) + orig_dst_pte = pte_mkuffd_wp(orig_dst_pte); set_pte_at(mm, dst_addr, dst_pte, orig_dst_pte); src_addr += PAGE_SIZE; -- 2.52.0