[PATCH net-next 03/12] net: hns3: fix a use after freed problem in hns3_nic_maybe_stop_tx()

[Huazhong Tan]

From: Yunsheng Lin <linyunsh...@huawei.com>

Currently, hns3_nic_maybe_stop_tx() use skb_copy() to linearize a
SKB if the BD num required by the SKB does not meet the hardware
limitation, and it linearizes the SKB by allocating a new SKB and
freeing the old SKB, if hns3_nic_maybe_stop_tx() returns -EBUSY,
the sch_direct_xmit() still hold reference to old SKB and try to
retransmit the old SKB when dev_hard_start_xmit() return TX_BUSY,
which may cause use after freed problem.

This patch fixes it by using __skb_linearize() to linearize the
SKB in hns3_nic_maybe_stop_tx().

Fixes: 51e8439f3496 ("net: hns3: add 8 BD limit for tx flow")
Signed-off-by: Yunsheng Lin <linyunsh...@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazh...@huawei.com>
---
 drivers/net/ethernet/hisilicon/hns3/hns3_enet.c | 19 ++++++-------------
 1 file changed, 6 insertions(+), 13 deletions(-)

diff --git a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c 
b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
index 2cfdfbb..5a237f94 100644
--- a/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
+++ b/drivers/net/ethernet/hisilicon/hns3/hns3_enet.c
@@ -1287,33 +1287,26 @@ static bool hns3_skb_need_linearized(struct sk_buff 
*skb, unsigned int *bd_size,
 }
 
 static int hns3_nic_maybe_stop_tx(struct net_device *netdev,
-                                 struct sk_buff **out_skb)
+                                 struct sk_buff *skb)
 {
        struct hns3_nic_priv *priv = netdev_priv(netdev);
        unsigned int bd_size[HNS3_MAX_TSO_BD_NUM + 1U];
-       struct sk_buff *skb = *out_skb;
        struct hns3_enet_ring *ring;
        unsigned int bd_num;
 
        ring = &priv->ring[skb->queue_mapping];
        bd_num = hns3_tx_bd_num(skb, bd_size);
        if (unlikely(bd_num > HNS3_MAX_NON_TSO_BD_NUM)) {
-               struct sk_buff *new_skb;
 
                if (bd_num <= HNS3_MAX_TSO_BD_NUM && skb_is_gso(skb) &&
                    !hns3_skb_need_linearized(skb, bd_size, bd_num))
                        goto out;
 
-               /* manual split the send packet */
-               new_skb = skb_copy(skb, GFP_ATOMIC);
-               if (!new_skb)
+               if (__skb_linearize(skb))
                        return -ENOMEM;
-               dev_kfree_skb_any(skb);
-               *out_skb = new_skb;
-
-               bd_num = hns3_tx_bd_count(new_skb->len);
-               if ((skb_is_gso(new_skb) && bd_num > HNS3_MAX_TSO_BD_NUM) ||
-                   (!skb_is_gso(new_skb) &&
+               bd_num = hns3_tx_bd_count(skb->len);
+               if ((skb_is_gso(skb) && bd_num > HNS3_MAX_TSO_BD_NUM) ||
+                   (!skb_is_gso(skb) &&
                     bd_num > HNS3_MAX_NON_TSO_BD_NUM))
                        return -ENOMEM;
 
@@ -1416,7 +1409,7 @@ netdev_tx_t hns3_nic_net_xmit(struct sk_buff *skb, struct 
net_device *netdev)
        /* Prefetch the data used later */
        prefetch(skb->data);
 
-       ret = hns3_nic_maybe_stop_tx(netdev, &skb);
+       ret = hns3_nic_maybe_stop_tx(netdev, skb);
        if (unlikely(ret <= 0)) {
                if (ret == -EBUSY) {
                        u64_stats_update_begin(&ring->syncp);
-- 
2.7.4