diff --git a/mm/mmap.c b/mm/mmap.c
index 322677f61d30..9a9933ede542 100644
--- a/mm/mmap.c
+++ b/mm/mmap.c
@@ -2652,7 +2652,7 @@ int do_munmap(struct mm_struct *mm, unsigned long start, size_t len,
 	return do_mas_munmap(&mas, mm, start, len, uf, false);
 }
 
-unsigned long mmap_region(struct file *file, unsigned long addr,
+static unsigned long __mmap_region(struct file *file, unsigned long addr,
 		unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
 		struct list_head *uf)
 {
@@ -2750,26 +2750,28 @@ cannot_expand:
 	vma->vm_page_prot = vm_get_page_prot(vm_flags);
 	vma->vm_pgoff = pgoff;
 
-	if (file) {
-		if (vm_flags & VM_SHARED) {
-			error = mapping_map_writable(file->f_mapping);
-			if (error)
-				goto free_vma;
-		}
+	if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
+		error = -ENOMEM;
+		goto free_vma;
+	}
 
+	if (file) {
 		vma->vm_file = get_file(file);
 		error = mmap_file(file, vma);
 		if (error)
-			goto unmap_and_free_vma;
+			goto unmap_and_free_file_vma;
+
+		/* Drivers cannot alter the address of the VMA. */
+		WARN_ON_ONCE(addr != vma->vm_start);
 
 		/*
-		 * Expansion is handled above, merging is handled below.
-		 * Drivers should not alter the address of the VMA.
+		 * Drivers should not permit writability when previously it was
+		 * disallowed.
 		 */
-		if (WARN_ON((addr != vma->vm_start))) {
-			error = -EINVAL;
-			goto close_and_free_vma;
-		}
+		VM_WARN_ON_ONCE(vm_flags != vma->vm_flags &&
+				!(vm_flags & VM_MAYWRITE) &&
+				(vma->vm_flags & VM_MAYWRITE));
+
 		mas_reset(&mas);
 
 		/*
@@ -2792,7 +2794,8 @@ cannot_expand:
 				vma = merge;
 				/* Update vm_flags to pick up the change. */
 				vm_flags = vma->vm_flags;
-				goto unmap_writable;
+				mas_destroy(&mas);
+				goto file_expanded;
 			}
 		}
 
@@ -2800,31 +2803,15 @@ cannot_expand:
 	} else if (vm_flags & VM_SHARED) {
 		error = shmem_zero_setup(vma);
 		if (error)
-			goto free_vma;
+			goto free_iter_vma;
 	} else {
 		vma_set_anonymous(vma);
 	}
 
-	/* Allow architectures to sanity-check the vm_flags */
-	if (!arch_validate_flags(vma->vm_flags)) {
-		error = -EINVAL;
-		if (file)
-			goto close_and_free_vma;
-		else if (vma->vm_file)
-			goto unmap_and_free_vma;
-		else
-			goto free_vma;
-	}
-
-	if (mas_preallocate(&mas, vma, GFP_KERNEL)) {
-		error = -ENOMEM;
-		if (file)
-			goto close_and_free_vma;
-		else if (vma->vm_file)
-			goto unmap_and_free_vma;
-		else
-			goto free_vma;
-	}
+#ifdef CONFIG_SPARC64
+	/* TODO: Fix SPARC ADI! */
+	WARN_ON_ONCE(!arch_validate_flags(vm_flags));
+#endif
 
 	if (vma->vm_file)
 		i_mmap_lock_write(vma->vm_file->f_mapping);
@@ -2847,10 +2834,7 @@ cannot_expand:
 	 */
 	khugepaged_enter_vma(vma, vma->vm_flags);
 
-	/* Once vma denies write, undo our temporary denial count */
-unmap_writable:
-	if (file && vm_flags & VM_SHARED)
-		mapping_unmap_writable(file->f_mapping);
+file_expanded:
 	file = vma->vm_file;
 expanded:
 	perf_event_mmap(vma);
@@ -2879,28 +2863,54 @@ expanded:
 
 	vma_set_page_prot(vma);
 
-	validate_mm(mm);
 	return addr;
 
-close_and_free_vma:
-	vma_close(vma);
-unmap_and_free_vma:
+unmap_and_free_file_vma:
 	fput(vma->vm_file);
 	vma->vm_file = NULL;
 
 	/* Undo any partial mapping done by a device driver. */
 	unmap_region(mm, mas.tree, vma, prev, next, vma->vm_start, vma->vm_end);
-	if (file && (vm_flags & VM_SHARED))
-		mapping_unmap_writable(file->f_mapping);
+free_iter_vma:
+	mas_destroy(&mas);
 free_vma:
 	vm_area_free(vma);
 unacct_error:
 	if (charged)
 		vm_unacct_memory(charged);
-	validate_mm(mm);
 	return error;
 }
 
+unsigned long mmap_region(struct file *file, unsigned long addr,
+			  unsigned long len, vm_flags_t vm_flags, unsigned long pgoff,
+			  struct list_head *uf)
+{
+	unsigned long ret;
+	bool writable_file_mapping = false;
+
+	/* Allow architectures to sanity-check the vm_flags. */
+	if (!arch_validate_flags(vm_flags))
+		return -EINVAL;
+
+	/* Map writable and ensure this isn't a sealed memfd. */
+	if (file && (vm_flags & VM_SHARED)) {
+		int error = mapping_map_writable(file->f_mapping);
+
+		if (error)
+			return error;
+		writable_file_mapping = true;
+	}
+
+	ret = __mmap_region(file, addr, len, vm_flags, pgoff, uf);
+
+	/* Clear our write mapping regardless of error. */
+	if (writable_file_mapping)
+		mapping_unmap_writable(file->f_mapping);
+
+	validate_mm(current->mm);
+	return ret;
+}
+
 static int __vm_munmap(unsigned long start, size_t len, bool downgrade)
 {
 	int ret;