# \[PATCH\] mlx4\_en: Fix read buffer overflow in mlx4\_en\_complete\_rx\_desc()

- From: Roel Kluin \<hidden\>
- Date: 2009-08-09 09:50:38 
- List: netdev
- Page: https://ratatoskr.run/netdev/2009/08/10828201

```text
If the length is less or equal to frag_prefix_size in the first iteration
we write skb_frags_rx[-1] and read from priv->frag_info[-1]

Signed-off-by: Roel Kluin <redacted>
---
diff --git a/drivers/net/mlx4/en_rx.c b/drivers/net/mlx4/en_rx.c
index 91bdfdf..3ac0404 100644
--- a/drivers/net/mlx4/en_rx.c
+++ b/drivers/net/mlx4/en_rx.c
@@ -506,8 +506,9 @@ static int mlx4_en_complete_rx_desc(struct mlx4_en_priv *priv,
 				 PCI_DMA_FROMDEVICE);
 	}
 	/* Adjust size of last fragment to match actual length */
-	skb_frags_rx[nr - 1].size = length -
-		priv->frag_info[nr - 1].frag_prefix_size;
+	if (nr > 0)
+		skb_frags_rx[nr - 1].size = length -
+			priv->frag_info[nr - 1].frag_prefix_size;
 	return nr;
 
 fail:
```