[PATCH net] net: hip04: fix RX buffer leak on build_skb failure

[Fan Wu <fanwu01@zju.edu.cn>]

When build_skb() fails in hip04_rx_poll(), the driver jumps to the
refill path without releasing the current RX buffer and its DMA mapping.
Installing a replacement buffer then overwrites the slot references and
leaks both resources.

Keep the current slot intact and return budget so NAPI retries the same
buffer.  Also free a newly allocated RX fragment when dma_map_single()
fails.

This issue was found by an in-house static analysis tool.

Fixes: 701a0fd52318 ("hip04_eth: fix missing error handle for build_skb failed")
Cc: stable@vger.kernel.org
Assisted-by: Codex:gpt-5.5
Signed-off-by: Fan Wu <fanwu01@zju.edu.cn>
---

 drivers/net/ethernet/hisilicon/hip04_eth.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hip04_eth.c b/drivers/net/ethernet/hisilicon/hip04_eth.c
index 18376bcc7..1d03039b4 100644
--- a/drivers/net/ethernet/hisilicon/hip04_eth.c
+++ b/drivers/net/ethernet/hisilicon/hip04_eth.c
@@ -594,7 +594,10 @@ static int hip04_rx_poll(struct napi_struct *napi, int budget)
 		skb = build_skb(buf, priv->rx_buf_size);
 		if (unlikely(!skb)) {
 			net_dbg_ratelimited("build_skb failed\n");
-			goto refill;
+			/* Retain the slot; return budget so NAPI retries this buffer.
+			 * Refill would overwrite rx_buf[]/rx_phys[] and leak them.
+			 */
+			return budget;
 		}
 
 		dma_unmap_single(priv->dev, priv->rx_phys[priv->rx_head],
@@ -622,14 +625,15 @@ static int hip04_rx_poll(struct napi_struct *napi, int budget)
 			rx++;
 		}
 
-refill:
 		buf = netdev_alloc_frag(priv->rx_buf_size);
 		if (!buf)
 			goto done;
 		phys = dma_map_single(priv->dev, buf,
 				      RX_BUF_SIZE, DMA_FROM_DEVICE);
-		if (dma_mapping_error(priv->dev, phys))
+		if (dma_mapping_error(priv->dev, phys)) {
+			skb_free_frag(buf);
 			goto done;
+		}
 		priv->rx_buf[priv->rx_head] = buf;
 		priv->rx_phys[priv->rx_head] = phys;
 		hip04_set_recv_desc(priv, phys);