[PATCH net] net: ethernet: mediatek: avoid potential invalid memory access

[sean.wang]

From: Sean Wang <sean.w...@mediatek.com>

Potential dangerous invalid memory might be accessed if invalid mac value
reflected from the forward port field in rxd4 caused by possible potential
hardware defects. So added a simple sanity checker to avoid the kind of
situation happening.

Signed-off-by: Sean Wang <sean.w...@mediatek.com>
---
 drivers/net/ethernet/mediatek/mtk_eth_soc.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/net/ethernet/mediatek/mtk_eth_soc.c 
b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
index c1dc08c..8175433 100644
--- a/drivers/net/ethernet/mediatek/mtk_eth_soc.c
+++ b/drivers/net/ethernet/mediatek/mtk_eth_soc.c
@@ -999,6 +999,12 @@ static int mtk_poll_rx(struct napi_struct *napi, int 
budget,
                      RX_DMA_FPORT_MASK;
                mac--;
 
+               if (unlikely(mac < 0 || mac >= MTK_MAC_COUNT ||
+                            !eth->netdev[mac])) {
+                       netdev->stats.rx_dropped++;
+                       goto release_desc;
+               }
+
                netdev = eth->netdev[mac];
 
                if (unlikely(test_bit(MTK_RESETTING, &eth->state)))
-- 
2.7.4