[hns3-0114]net: hns3: fix a use after free problem in hns3_nic_maybe_stop_tx()

[Fred Kimmy]

[Bug Description]
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 linearized SKB
and freeing the old SKB, if hns3_nic_maybe_stop_tx() returns -EBUSY
because there are no enough space in the ring to send the linearized
skb to hardware, 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.

[Steps to Reproduce]
1.run IO with high throughput

[Actual Results]
Oops

[Expected Results]
IO ok

[Reproducibility]
Inevitably

[Additional information]
Hardware: D06
Firmware: NA
Kernel: NA

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

d1a37dedcfcf net: hns3: fix a use after free problem in hns3_nic_maybe_stop_tx()

[Ike Panhc (ikepanhc)]

Unable to cherry-pick for bionic kernel.

[Ike Panhc (ikepanhc)]

In focal kernel since 5.4.0-13.16