tcp: Fix a data-race around sysctl_tcp_early_retrans.

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

Fixes: eed530b6c676 ("tcp: early retransmit")
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 38a71e7..898fcdc 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -2741,7 +2741,7 @@ bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto)
        if (rcu_access_pointer(tp->fastopen_rsk))
                return false;
 
-       early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans;
+       early_retrans = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_early_retrans);
        /* Schedule a loss probe in 2*RTT for SACK capable connections
         * not in loss recovery, that are either limited by cwnd or application.
         */