1 files changed, 24 insertions, 25 deletions

diff --git a/mm/userfaultfd.c b/mm/userfaultfd.c
index 0499907b6f1a..53c3d916ff66 100644
--- a/mm/userfaultfd.c
+++ b/mm/userfaultfd.c
@@ -74,24 +74,10 @@ int mfill_atomic_install_pte(struct mm_struct *dst_mm, pmd_t *dst_pmd,
 	_dst_pte = pte_mkdirty(_dst_pte);
 	if (page_in_cache && !vm_shared)
 		writable = false;
-
-	/*
-	 * Always mark a PTE as write-protected when needed, regardless of
-	 * VM_WRITE, which the user might change.
-	 */
-	if (wp_copy) {
-		_dst_pte = pte_mkuffd_wp(_dst_pte);
-		writable = false;
-	}
-
 	if (writable)
 		_dst_pte = pte_mkwrite(_dst_pte);
-	else
-		/*
-		 * We need this to make sure write bit removed; as mk_pte()
-		 * could return a pte with write bit set.
-		 */
-		_dst_pte = pte_wrprotect(_dst_pte);
+	if (wp_copy)
+		_dst_pte = pte_mkuffd_wp(_dst_pte);
 
 	dst_pte = pte_offset_map_lock(dst_mm, dst_pmd, dst_addr, &ptl);
 
@@ -724,21 +710,31 @@ ssize_t mcopy_continue(struct mm_struct *dst_mm, unsigned long start,
 			      mmap_changing, 0);
 }
 
-void uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma,
+long uffd_wp_range(struct mm_struct *dst_mm, struct vm_area_struct *dst_vma,
 		   unsigned long start, unsigned long len, bool enable_wp)
 {
+	unsigned int mm_cp_flags;
 	struct mmu_gather tlb;
-	pgprot_t newprot;
+	long ret;
 
 	if (enable_wp)
-		newprot = vm_get_page_prot(dst_vma->vm_flags & ~(VM_WRITE));
+		mm_cp_flags = MM_CP_UFFD_WP;
 	else
-		newprot = vm_get_page_prot(dst_vma->vm_flags);
+		mm_cp_flags = MM_CP_UFFD_WP_RESOLVE;
 
+	/*
+	 * vma->vm_page_prot already reflects that uffd-wp is enabled for this
+	 * VMA (see userfaultfd_set_vm_flags()) and that all PTEs are supposed
+	 * to be write-protected as default whenever protection changes.
+	 * Try upgrading write permissions manually.
+	 */
+	if (!enable_wp && vma_wants_manual_pte_write_upgrade(dst_vma))
+		mm_cp_flags |= MM_CP_TRY_CHANGE_WRITABLE;
 	tlb_gather_mmu(&tlb, dst_mm);
-	change_protection(&tlb, dst_vma, start, start + len, newprot,
-			  enable_wp ? MM_CP_UFFD_WP : MM_CP_UFFD_WP_RESOLVE);
+	ret = change_protection(&tlb, dst_vma, start, start + len, mm_cp_flags);
 	tlb_finish_mmu(&tlb);
+
+	return ret;
 }
 
 int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
@@ -747,7 +743,7 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
 {
 	struct vm_area_struct *dst_vma;
 	unsigned long page_mask;
-	int err;
+	long err;
 
 	/*
 	 * Sanitize the command parameters:
@@ -786,9 +782,12 @@ int mwriteprotect_range(struct mm_struct *dst_mm, unsigned long start,
 			goto out_unlock;
 	}
 
-	uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp);
+	err = uffd_wp_range(dst_mm, dst_vma, start, len, enable_wp);
+
+	/* Return 0 on success, <0 on failures */
+	if (err > 0)
+		err = 0;
 
-	err = 0;
 out_unlock:
 	mmap_read_unlock(dst_mm);
 	return err;