net: ftgmac100: fix ring allocation unwind on open failure

ftgmac100_alloc_rings() allocates rx_skbs, tx_skbs, rxdes, txdes, and
rx_scratch in stages. On intermediate failures it returned -ENOMEM
directly, leaking resources allocated earlier in the function.

Rework the failure path to use staged local unwind labels and free
allocated resources in reverse order before returning -ENOMEM. This
matches common netdev allocation cleanup style.

Fixes: d72e01a ("ftgmac100: Use a scratch buffer for failed RX allocations")
Cc: stable@vger.kernel.org
Signed-off-by: Yufan Chen <yufan.chen@linux.dev>
Link: https://patch.msgid.link/20260328163257.60836-1-yufan.chen@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: Eric-Terminal

drivers/net/ethernet/faraday/ftgmac100.c

@@ -977,29 +977,49 @@ static int ftgmac100_alloc_rings(struct ftgmac100 *priv)
 	priv->tx_skbs = kcalloc(MAX_TX_QUEUE_ENTRIES, sizeof(void *),
 				GFP_KERNEL);
 	if (!priv->tx_skbs)
-		return -ENOMEM;
+		goto err_free_rx_skbs;
 
 	/* Allocate descriptors */
 	priv->rxdes = dma_alloc_coherent(priv->dev,
 					 MAX_RX_QUEUE_ENTRIES * sizeof(struct ftgmac100_rxdes),
 					 &priv->rxdes_dma, GFP_KERNEL);
 	if (!priv->rxdes)
-		return -ENOMEM;
+		goto err_free_tx_skbs;
 	priv->txdes = dma_alloc_coherent(priv->dev,
 					 MAX_TX_QUEUE_ENTRIES * sizeof(struct ftgmac100_txdes),
 					 &priv->txdes_dma, GFP_KERNEL);
 	if (!priv->txdes)
-		return -ENOMEM;
+		goto err_free_rxdes;
 
 	/* Allocate scratch packet buffer */
 	priv->rx_scratch = dma_alloc_coherent(priv->dev,
 					      RX_BUF_SIZE,
 					      &priv->rx_scratch_dma,
 					      GFP_KERNEL);
 	if (!priv->rx_scratch)
-		return -ENOMEM;
+		goto err_free_txdes;
 
 	return 0;
+
+err_free_txdes:
+	dma_free_coherent(priv->dev,
+			  MAX_TX_QUEUE_ENTRIES *
+			  sizeof(struct ftgmac100_txdes),
+			  priv->txdes, priv->txdes_dma);
+	priv->txdes = NULL;
+err_free_rxdes:
+	dma_free_coherent(priv->dev,
+			  MAX_RX_QUEUE_ENTRIES *
+			  sizeof(struct ftgmac100_rxdes),
+			  priv->rxdes, priv->rxdes_dma);
+	priv->rxdes = NULL;
+err_free_tx_skbs:
+	kfree(priv->tx_skbs);
+	priv->tx_skbs = NULL;
+err_free_rx_skbs:
+	kfree(priv->rx_skbs);
+	priv->rx_skbs = NULL;
+	return -ENOMEM;
 }
 
 static void ftgmac100_init_rings(struct ftgmac100 *priv)