icmp: Fix data-races around sysctl.

stable inclusion
from stable-4.19.253
commit edeec63b13c252193d626c2a48d7a2f0e7016dc2
category: bugfix
bugzilla: https://gitee.com/openeuler/kernel/issues/I5I4FP


CVE: NA

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[ Upstream commit 48d7ee32 ]

While reading icmp sysctl variables, they can be changed concurrently.
So, we need to add READ_ONCE() to avoid data-races.

Fixes: 4cdf507d ("icmp: add a global rate limitation")
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>