contrib/vhost-user-blk: avoid g_return_val_if() input validation

Do not validate input with g_return_val_if(). This API is intended for
checking programming errors and is compiled out with -DG_DISABLE_CHECKS.

Use an explicit if statement for input validation so it cannot
accidentally be compiled out.

Suggested-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20201118091644.199527-2-stefanha@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

contrib/vhost-user-blk/vhost-user-blk.c

@@ -403,7 +403,9 @@ vub_get_config(VuDev *vu_dev, uint8_t *config, uint32_t len)
     VugDev *gdev;
     VubDev *vdev_blk;
 
-    g_return_val_if_fail(len <= sizeof(struct virtio_blk_config), -1);
+    if (len > sizeof(struct virtio_blk_config)) {
+        return -1;
+    }
 
     gdev = container_of(vu_dev, VugDev, parent);
     vdev_blk = container_of(gdev, VubDev, parent);