Merge branch 'for-next' into for-linus

1 files changed, 18 insertions, 6 deletions

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 5d05093014ac..da45215a933d 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -126,7 +126,6 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 	void __user *user_bo_handles = NULL;
 	struct virtio_gpu_object_array *buflist = NULL;
 	struct sync_file *sync_file;
-	int in_fence_fd = exbuf->fence_fd;
 	int out_fence_fd = -1;
 	void *buf;
 	uint64_t fence_ctx;
@@ -152,13 +151,11 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
 		ring_idx = exbuf->ring_idx;
 	}
 
-	exbuf->fence_fd = -1;
-
 	virtio_gpu_create_context(dev, file);
 	if (exbuf->flags & VIRTGPU_EXECBUF_FENCE_FD_IN) {
 		struct dma_fence *in_fence;
 
-		in_fence = sync_file_get_fence(in_fence_fd);
+		in_fence = sync_file_get_fence(exbuf->fence_fd);
 
 		if (!in_fence)
 			return -EINVAL;
@@ -358,10 +355,18 @@ static int virtio_gpu_resource_create_ioctl(struct drm_device *dev, void *data,
 		drm_gem_object_release(obj);
 		return ret;
 	}
-	drm_gem_object_put(obj);
 
 	rc->res_handle = qobj->hw_res_handle; /* similiar to a VM address */
 	rc->bo_handle = handle;
+
+	/*
+	 * The handle owns the reference now.  But we must drop our
+	 * remaining reference *after* we no longer need to dereference
+	 * the obj.  Otherwise userspace could guess the handle and
+	 * race closing it from another thread.
+	 */
+	drm_gem_object_put(obj);
+
 	return 0;
 }
 
@@ -723,11 +728,18 @@ static int virtio_gpu_resource_create_blob_ioctl(struct drm_device *dev,
 		drm_gem_object_release(obj);
 		return ret;
 	}
-	drm_gem_object_put(obj);
 
 	rc_blob->res_handle = bo->hw_res_handle;
 	rc_blob->bo_handle = handle;
 
+	/*
+	 * The handle owns the reference now.  But we must drop our
+	 * remaining reference *after* we no longer need to dereference
+	 * the obj.  Otherwise userspace could guess the handle and
+	 * race closing it from another thread.
+	 */
+	drm_gem_object_put(obj);
+
 	return 0;
 }