ethernet:enic: Fix a use after free bug in enic_hard_start_xmit

stable inclusion
from stable-v4.19.191
commit 25a87b1f566b5eb2af2857a928f0e2310d900976
category: bugfix
bugzilla: https://gitee.com/src-openeuler/kernel/issues/I94JCD
CVE: CVE-2021-46998

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=25a87b1f566b5eb2af2857a928f0e2310d900976

---------------------------

[ Upstream commit 643001b4 ]

In enic_hard_start_xmit, it calls enic_queue_wq_skb(). Inside
enic_queue_wq_skb, if some error happens, the skb will be freed
by dev_kfree_skb(skb). But the freed skb is still used in
skb_tx_timestamp(skb).

My patch makes enic_queue_wq_skb() return error and goto spin_unlock()
incase of error. The solution is provided by Govind.
See https://lkml.org/lkml/2021/4/30/961

.

Fixes: fb7516d4 ("enic: add sw timestamp support")
Signed-off-by: Lv Yunlong <lyl2019@mail.ustc.edu.cn>
Acked-by: Govindarajulu Varadarajan <gvaradar@cisco.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Liu Jian <liujian56@huawei.com>