tcp: Fix data-races around sk_pacing_rate.

[ Upstream commit 59bf6c65a09fff74215517aecffbbdcd67df76e3 ] While reading sysctl_tcp_pacing_(ss|ca)_ratio, they can be changed concurrently. Thus, we need to add READ_ONCE() to their readers. Fixes: 43e122b ("tcp: refine pacing rate determination") 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>

Author: q2ven

net/ipv4/tcp_input.c

@@ -902,9 +902,9 @@ static void tcp_update_pacing_rate(struct sock *sk)
  * end of slow start and should slow down.
  */
 if (tcp_snd_cwnd(tp) < tp->snd_ssthresh / 2)
-rate *= sock_net(sk)->ipv4.sysctl_tcp_pacing_ss_ratio;
+rate *= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_pacing_ss_ratio);
 else
-rate *= sock_net(sk)->ipv4.sysctl_tcp_pacing_ca_ratio;
+rate *= READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_pacing_ca_ratio);
 
 rate *= max(tcp_snd_cwnd(tp), tp->packets_out);