tcp: Fix a data-race around sysctl_tcp_thin_linear_timeouts.

stable inclusion
from stable-v4.19.254
commit f4b0295be9a3c4260de4585fac4062e602a88ac7
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5Q0SQ


CVE: NA

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[ Upstream commit 7c6f2a86 ]

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

Fixes: 36e31b0a ("net: TCP thin linear timeouts")
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>