Merge branch 'net-spacemit-a-few-error-handling-fixes'

Vivian Wang says:

====================
net: spacemit: A few error handling fixes

Recently a user reported a supposed UAF/double-free in this driver.
It turned out to be a false positive (ugh) from a bug with riscv's
kfence_protect_page() [1], but it did also prompt me to review the
driver code yet again. These are some fixes for error handling problems
that I've found.

[1]: https://lore.kernel.org/r/20260303-handle-kfence-protect-spurious-fault-v2-0-f80d8354d79d@iscas.ac.cn/
====================

Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

Author: kuba-moo

drivers/net/ethernet/spacemit/k1_emac.c

@@ -565,7 +565,9 @@ static void emac_alloc_rx_desc_buffers(struct emac_priv *priv)
 						  DMA_FROM_DEVICE);
 		if (dma_mapping_error(&priv->pdev->dev, rx_buf->dma_addr)) {
 			dev_err_ratelimited(&ndev->dev, "Mapping skb failed\n");
-			goto err_free_skb;
+			dev_kfree_skb_any(skb);
+			rx_buf->skb = NULL;
+			break;
 		}
 
 		rx_desc_addr = &((struct emac_desc *)rx_ring->desc_addr)[i];
@@ -590,10 +592,6 @@ static void emac_alloc_rx_desc_buffers(struct emac_priv *priv)
 
 	rx_ring->head = i;
 	return;
-
-err_free_skb:
-	dev_kfree_skb_any(skb);
-	rx_buf->skb = NULL;
 }
 
 /* Returns number of packets received */
@@ -735,7 +733,7 @@ static void emac_tx_mem_map(struct emac_priv *priv, struct sk_buff *skb)
 	struct emac_desc tx_desc, *tx_desc_addr;
 	struct device *dev = &priv->pdev->dev;
 	struct emac_tx_desc_buffer *tx_buf;
-	u32 head, old_head, frag_num, f;
+	u32 head, old_head, frag_num, f, i;
 	bool buf_idx;
 
 	frag_num = skb_shinfo(skb)->nr_frags;
@@ -803,6 +801,15 @@ static void emac_tx_mem_map(struct emac_priv *priv, struct sk_buff *skb)
 
 err_free_skb:
 	dev_dstats_tx_dropped(priv->ndev);
+
+	i = old_head;
+	while (i != head) {
+		emac_free_tx_buf(priv, i);
+
+		if (++i == tx_ring->total_cnt)
+			i = 0;
+	}
+
 	dev_kfree_skb_any(skb);
 }