tcp: Fix data-races around sysctl_tcp_fastopen_blackhole_timeout.

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

Fixes: b2194934b7e8 ("net/tcp_fastopen: Disable active side TFO in certain scenarios")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 0acdb5473850df97bc1961e01da5f413d9ced321..825b216d11f52bc79a29b7a696005175a55a6804 100644 (file)
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -489,7 +489,7 @@ void tcp_fastopen_active_disable(struct sock *sk)
 {
        struct net *net = sock_net(sk);
 
-       if (!sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout)
+       if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout))
                return;
 
        /* Paired with READ_ONCE() in tcp_fastopen_active_should_disable() */
@@ -510,7 +510,8 @@ void tcp_fastopen_active_disable(struct sock *sk)
  */
 bool tcp_fastopen_active_should_disable(struct sock *sk)
 {
-       unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;
+       unsigned int tfo_bh_timeout =
+               READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout);
        unsigned long timeout;
        int tfo_da_times;
        int multiplier;