tcp: Fix a data-race around sysctl_tcp_tso_rtt_log.

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

Fixes: 754647c28d8e ("tcp: adjust TSO packet sizes based on min_rtt")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 6e29cf391a645d0fb5c2ce94d36f27422dba3cb7..cf6713c9567e14feab0c7f7b908f6653b6e19672 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1976,7 +1976,7 @@ static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now,
 
        bytes = sk->sk_pacing_rate >> READ_ONCE(sk->sk_pacing_shift);
 
-       r = tcp_min_rtt(tcp_sk(sk)) >> sock_net(sk)->ipv4.sysctl_tcp_tso_rtt_log;
+       r = tcp_min_rtt(tcp_sk(sk)) >> READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_rtt_log);
        if (r < BITS_PER_TYPE(sk->sk_gso_max_size))
                bytes += sk->sk_gso_max_size >> r;