tcp: Fix data-races around sysctl_tcp_slow_start_after_idle.

[ Upstream commit 4845b5713ab18a1bb6e31d1fbb4d600240b8b691 ]

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

Fixes: 35089bb203f4 ("[TCP]: Add tcp_slow_start_after_idle sysctl.")
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>

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 0c609d1..8ce8aaf 100644 (file)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1390,8 +1390,8 @@ static inline void tcp_slow_start_after_idle_check(struct sock *sk)
        struct tcp_sock *tp = tcp_sk(sk);
        s32 delta;
 
-       if (!sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle || tp->packets_out ||
-           ca_ops->cong_control)
+       if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle) ||
+           tp->packets_out || ca_ops->cong_control)
                return;
        delta = tcp_jiffies32 - tp->lsndtime;
        if (delta > inet_csk(sk)->icsk_rto)

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 3b71d87..94f7841 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1901,7 +1901,7 @@ static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited)
                if (tp->packets_out > tp->snd_cwnd_used)
                        tp->snd_cwnd_used = tp->packets_out;
 
-               if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle &&
+               if (READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle) &&
                    (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto &&
                    !ca_ops->cong_control)
                        tcp_cwnd_application_limited(sk);