drm/vmwgfx: Tighten the security around buffer maps

Make sure that other DRM clients can't map the contents of
non-shareable buffer objects.
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/gpu/drm/vmwgfx/vmwgfx_buffer.c

@@ -248,13 +248,12 @@ void vmw_evict_flags(struct ttm_buffer_object *bo,
 	*placement = vmw_sys_placement;
 }
 
-/**
- * FIXME: Proper access checks on buffers.
- */
-
 static int vmw_verify_access(struct ttm_buffer_object *bo, struct file *filp)
 {
-	return 0;
+	struct ttm_object_file *tfile =
+		vmw_fpriv((struct drm_file *)filp->private_data)->tfile;
+
+	return vmw_user_dmabuf_verify_access(bo, tfile);
 }
 
 static int vmw_ttm_io_mem_reserve(struct ttm_bo_device *bdev, struct ttm_mem_reg *mem)

drivers/gpu/drm/vmwgfx/vmwgfx_drv.h

@@ -461,6 +461,8 @@ extern int vmw_dmabuf_init(struct vmw_private *dev_priv,
 			   size_t size, struct ttm_placement *placement,
 			   bool interuptable,
 			   void (*bo_free) (struct ttm_buffer_object *bo));
+extern int vmw_user_dmabuf_verify_access(struct ttm_buffer_object *bo,
+				  struct ttm_object_file *tfile);
 extern int vmw_dmabuf_alloc_ioctl(struct drm_device *dev, void *data,
 				  struct drm_file *file_priv);
 extern int vmw_dmabuf_unref_ioctl(struct drm_device *dev, void *data,

drivers/gpu/drm/vmwgfx/vmwgfx_resource.c

@@ -458,6 +458,26 @@ int vmw_user_dmabuf_alloc(struct vmw_private *dev_priv,
 	return ret;
 }
 
+/**
+ * vmw_user_dmabuf_verify_access - verify access permissions on this
+ * buffer object.
+ *
+ * @bo: Pointer to the buffer object being accessed
+ * @tfile: Identifying the caller.
+ */
+int vmw_user_dmabuf_verify_access(struct ttm_buffer_object *bo,
+				  struct ttm_object_file *tfile)
+{
+	struct vmw_user_dma_buffer *vmw_user_bo;
+
+	if (unlikely(bo->destroy != vmw_user_dmabuf_destroy))
+		return -EPERM;
+
+	vmw_user_bo = vmw_user_dma_buffer(bo);
+	return (vmw_user_bo->base.tfile == tfile ||
+	vmw_user_bo->base.shareable) ? 0 : -EPERM;
+}
+
 int vmw_dmabuf_alloc_ioctl(struct drm_device *dev, void *data,
 			   struct drm_file *file_priv)
 {