mlx4_en: Fix read buffer overflow in mlx4_en_complete_rx_desc()

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 <roel.kluin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/drivers/net/mlx4/en_rx.c b/drivers/net/mlx4/en_rx.c
index 91bdfdfd431..3ac0404d0d1 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: