netdev - [PATCH V2] amd-xgbe: set skb to NULL after freeing it

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Date:   Wed, 28 Nov 2018 17:06:15 +0800
From:   Pan Bian <bianpan2016@....com>
To:     Tom Lendacky <thomas.lendacky@....com>,
        "David S. Miller" <davem@...emloft.net>
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Pan Bian <bianpan2016@....com>
Subject: [PATCH V2] amd-xgbe: set skb to NULL after freeing it

The buffer skb is freed via dev_kfree_skb in a loop. After freeing skb, 
the value of packet_count is updated via packet_count++. If packet_count
happens to equal the upper bound budget, the loop will be broken and skb 
may be assigned to rdata->state.skb. Resulting that rdata->state.skb may
point to a freed memory chunk. To fix this, the patch sets skb to NULL 
after dev_kfree_skb(skb).

Signed-off-by: Pan Bian <bianpan2016@....com>
---
V2: correct the commit log
---
 drivers/net/ethernet/amd/xgbe/xgbe-drv.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
index 0cc911f..ac6b82d 100644
--- a/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
+++ b/drivers/net/ethernet/amd/xgbe/xgbe-drv.c
@@ -2754,6 +2754,7 @@ static int xgbe_rx_poll(struct xgbe_channel *channel, int budget)
 				netif_err(pdata, rx_err, netdev,
 					  "error in received packet\n");
 			dev_kfree_skb(skb);
+			skb = NULL;
 			goto next_packet;
 		}
 
@@ -2806,6 +2807,7 @@ static int xgbe_rx_poll(struct xgbe_channel *channel, int budget)
 			netif_err(pdata, rx_err, netdev,
 				  "packet length exceeds configured MTU\n");
 			dev_kfree_skb(skb);
+			skb = NULL;
 			goto next_packet;
 		}
 
-- 
2.7.4