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Subject[PATCH net 2/3] net: hns3: fix a use after free problem in hns3_nic_maybe_stop_tx()
Date
From: Yunsheng Lin <linyunsheng@huawei.com>

Currently, hns3_nic_maybe_stop_tx() uses 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 <linyunsheng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@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 b2bb8e2..cbdb688 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
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