bgmac: fix a missing check for build_skb

[Weidong Wang]

when build_skb failed, it may occure a NULL pointer.
So add a 'NULL check' for it.

Signed-off-by: Weidong Wang <wangweidong1@xxxxxxxxxx>
---
 drivers/net/ethernet/broadcom/bgmac.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/ethernet/broadcom/bgmac.c b/drivers/net/ethernet/broadcom/bgmac.c
index 21e3c38..d75180a 100644
--- a/drivers/net/ethernet/broadcom/bgmac.c
+++ b/drivers/net/ethernet/broadcom/bgmac.c
@@ -466,6 +466,11 @@ static int bgmac_dma_rx_read(struct bgmac *bgmac, struct bgmac_dma_ring *ring,
 			len -= ETH_FCS_LEN;

 			skb = build_skb(buf, BGMAC_RX_ALLOC_SIZE);
+			if (unlikely(skb)) {
+				bgmac_err(bgmac, "build_skb failed\n");
+				put_page(virt_to_head_page(buf));
+				break;
+			}
 			skb_put(skb, BGMAC_RX_FRAME_OFFSET +
 				BGMAC_RX_BUF_OFFSET + len);
 			skb_pull(skb, BGMAC_RX_FRAME_OFFSET +
-- 
1.9.0