drm/rockchip: use drm_gem_mmap helpers

commit 41315b79 upstream.

Rather than (incompletely [0]) re-implementing drm_gem_mmap() and
drm_gem_mmap_obj() helpers, call them directly from the rockchip mmap
routines.

Once the core functions return successfully, the rockchip mmap routines
can still use dma_mmap_attrs() to simply mmap the entire buffer.

[0] Previously, we were performing the mmap() without first taking a
reference on the underlying gem buffer.  This could leak ptes if the gem
object is destroyed while userspace is still holding the mapping.
Signed-off-by: Daniel Kurtz <djkurtz@chromium.org>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/gpu/drm/rockchip/rockchip_drm_gem.c

@@ -54,55 +54,56 @@ static void rockchip_gem_free_buf(struct rockchip_gem_object *rk_obj)
 		       &rk_obj->dma_attrs);
 }
 
-int rockchip_gem_mmap_buf(struct drm_gem_object *obj,
-			  struct vm_area_struct *vma)
+static int rockchip_drm_gem_object_mmap(struct drm_gem_object *obj,
+					struct vm_area_struct *vma)
+
 {
+	int ret;
 	struct rockchip_gem_object *rk_obj = to_rockchip_obj(obj);
 	struct drm_device *drm = obj->dev;
-	unsigned long vm_size;
 
-	vma->vm_flags |= VM_IO | VM_DONTEXPAND | VM_DONTDUMP;
-	vm_size = vma->vm_end - vma->vm_start;
-
-	if (vm_size > obj->size)
-		return -EINVAL;
+	/*
+	 * dma_alloc_attrs() allocated a struct page table for rk_obj, so clear
+	 * VM_PFNMAP flag that was set by drm_gem_mmap_obj()/drm_gem_mmap().
+	 */
+	vma->vm_flags &= ~VM_PFNMAP;
 
-	return dma_mmap_attrs(drm->dev, vma, rk_obj->kvaddr, rk_obj->dma_addr,
+	ret = dma_mmap_attrs(drm->dev, vma, rk_obj->kvaddr, rk_obj->dma_addr,
 			     obj->size, &rk_obj->dma_attrs);
+	if (ret)
+		drm_gem_vm_close(vma);
+
+	return ret;
 }
 
-/* drm driver mmap file operations */
-int rockchip_gem_mmap(struct file *filp, struct vm_area_struct *vma)
+int rockchip_gem_mmap_buf(struct drm_gem_object *obj,
+			  struct vm_area_struct *vma)
 {
-	struct drm_file *priv = filp->private_data;
-	struct drm_device *dev = priv->minor->dev;
-	struct drm_gem_object *obj;
-	struct drm_vma_offset_node *node;
+	struct drm_device *drm = obj->dev;
 	int ret;
 
-	if (drm_device_is_unplugged(dev))
-		return -ENODEV;
+	mutex_lock(&drm->struct_mutex);
+	ret = drm_gem_mmap_obj(obj, obj->size, vma);
+	mutex_unlock(&drm->struct_mutex);
+	if (ret)
+		return ret;
 
-	mutex_lock(&dev->struct_mutex);
+	return rockchip_drm_gem_object_mmap(obj, vma);
+}
 
-	node = drm_vma_offset_exact_lookup(dev->vma_offset_manager,
-					   vma->vm_pgoff,
-					   vma_pages(vma));
-	if (!node) {
-		mutex_unlock(&dev->struct_mutex);
-		DRM_ERROR("failed to find vma node.\n");
-		return -EINVAL;
-	} else if (!drm_vma_node_is_allowed(node, filp)) {
-		mutex_unlock(&dev->struct_mutex);
-		return -EACCES;
-	}
+/* drm driver mmap file operations */
+int rockchip_gem_mmap(struct file *filp, struct vm_area_struct *vma)
+{
+	struct drm_gem_object *obj;
+	int ret;
 
-	obj = container_of(node, struct drm_gem_object, vma_node);
-	ret = rockchip_gem_mmap_buf(obj, vma);
+	ret = drm_gem_mmap(filp, vma);
+	if (ret)
+		return ret;
 
-	mutex_unlock(&dev->struct_mutex);
+	obj = vma->vm_private_data;
 
-	return ret;
+	return rockchip_drm_gem_object_mmap(obj, vma);
 }
 
 struct rockchip_gem_object *