tcp: Fix a data-race around sysctl_tcp_min_tso_segs.

stable inclusion
from stable-v4.19.255
commit 15085721749ad8d3063a54252d974a24a9751c15
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5Q0SQ


CVE: NA

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

[ Upstream commit e0bb4ab9dfddd872622239f49fb2bd403b70853b ]

While reading sysctl_tcp_min_tso_segs, it can be changed concurrently.
Thus, we need to add READ_ONCE() to its reader.

Fixes: 95bd09eb ("tcp: TSO packets automatic sizing")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com>