[PATCH net] net: fec: Coverity issue: Dereference null return value

[wei . fang]

From: Wei Fang <wei.fang@xxxxxxx>

The build_skb might return a null pointer but there is no check on the
return value in the fec_enet_rx_queue(). So a null pointer dereference
might occur. To avoid this, we check the return value of build_skb. If
the return value is a null pointer, the driver will recycle the page and
update the statistic of ndev. Then jump to rx_processing_done to clear
the status flags of the BD so that the hardware can recycle the BD.

Signed-off-by: Wei Fang <wei.fang@xxxxxxx>
Reviewed-by: Shenwei Wang <Shenwei.wang@xxxxxxx>
---
 drivers/net/ethernet/freescale/fec_main.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/net/ethernet/freescale/fec_main.c b/drivers/net/ethernet/freescale/fec_main.c
index 5528b0af82ae..c78aaa780983 100644
--- a/drivers/net/ethernet/freescale/fec_main.c
+++ b/drivers/net/ethernet/freescale/fec_main.c
@@ -1674,6 +1674,16 @@ fec_enet_rx_queue(struct net_device *ndev, int budget, u16 queue_id)
 		 * bridging applications.
 		 */
 		skb = build_skb(page_address(page), PAGE_SIZE);
+		if (unlikely(!skb)) {
+			page_pool_recycle_direct(rxq->page_pool, page);
+			ndev->stats.rx_packets--;
+			ndev->stats.rx_bytes -= pkt_len;
+			ndev->stats.rx_dropped++;
+
+			netdev_err(ndev, "build_skb failed!\n");
+			goto rx_processing_done;
+		}
+
 		skb_reserve(skb, data_start);
 		skb_put(skb, pkt_len - sub_len);
 		skb_mark_for_recycle(skb);
-- 
2.25.1