net: stmmac: fix potential double free of dma descriptor resources

LoongArch inclusion
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I733VA

--------------------------------

reset the dma descriptor related resource's pointer to NULL,otherwise
a potential double free problem may be triggered:
stmmac_open
  alloc_dma_desc_resources
  init_dma_desc_rings
  stmmac_hw_setup  (Failed)
    goto init_error;
  free_dma_desc_resources(priv);
  (DMA related resource pointer not reset to NULL)
...
stmmac_open
  alloc_dma_desc_resources
    alloc_dma_tx_desc_resources (Failed)
      free_dma_tx_desc_resources
      (Double free of tx_q->tx_skbuff_dma tx_q->tx_skbuff)
Signed-off-by: NHongchen Zhang <zhanghongchen@loongson.cn>
Change-Id: Ie917b7402e86cbd1b253553c10ac4a5440e38c03

drivers/net/ethernet/stmicro/stmmac/stmmac_main.c

@@ -1635,10 +1635,15 @@ static void free_dma_rx_desc_resources(struct stmmac_priv *priv)
 			dma_free_coherent(priv->device, priv->dma_rx_size *
 					  sizeof(struct dma_extended_desc),
 					  rx_q->dma_erx, rx_q->dma_rx_phy);
+		rx_q->dma_rx = NULL;
+		rx_q->dma_erx = NULL;
 
 		kfree(rx_q->buf_pool);
+		rx_q->buf_pool = NULL;
+
 		if (rx_q->page_pool)
 			page_pool_destroy(rx_q->page_pool);
+		rx_q->page_pool = NULL;
 	}
 }
 
@@ -1675,8 +1680,15 @@ static void free_dma_tx_desc_resources(struct stmmac_priv *priv)
 
 		dma_free_coherent(priv->device, size, addr, tx_q->dma_tx_phy);
 
+		tx_q->dma_etx = NULL;
+		tx_q->dma_entx = NULL;
+		tx_q->dma_tx = NULL;
+
 		kfree(tx_q->tx_skbuff_dma);
+		tx_q->tx_skbuff_dma = NULL;
+
 		kfree(tx_q->tx_skbuff);
+		tx_q->tx_skbuff = NULL;
 	}
 }