ethtool: fix error handling in linkstate_prepare_data()

When getting SQI or maximum SQI value fails in linkstate_prepare_data(), we
must not return without calling ethnl_ops_complete(dev) as that could
result in imbalance between ethtool_ops ->begin() and ->complete() calls.

Fixes: 80660219 ("ethtool: provide UAPI for PHY Signal Quality Index (SQI)")
Signed-off-by: NMichal Kubecek <mkubecek@suse.cz>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ethtool/linkstate.c

@@ -78,19 +78,18 @@ static int linkstate_prepare_data(const struct ethnl_req_info *req_base,
 
 	ret = linkstate_get_sqi(dev);
 	if (ret < 0 && ret != -EOPNOTSUPP)
-		return ret;
-
+		goto out;
 	data->sqi = ret;
 
 	ret = linkstate_get_sqi_max(dev);
 	if (ret < 0 && ret != -EOPNOTSUPP)
-		return ret;
-
+		goto out;
 	data->sqi_max = ret;
 
+	ret = 0;
+out:
 	ethnl_ops_complete(dev);
-
-	return 0;
+	return ret;
 }
 
 static int linkstate_reply_size(const struct ethnl_req_info *req_base,