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>

1 files changed, 20 insertions, 0 deletions

diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
index 88b6f921ee94..0def4ff5b621 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_resource.c
@@ -458,6 +458,26 @@ out_no_base_object:
         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)
 {