tcp: Fix data-races around sysctl_tcp_fastopen_blackhole_timeout.

[ Upstream commit 021266ec640c7a4527e6cd4b7349a512b351de1d ]

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

Fixes: cf1ef3f0719b ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index 936544a4753e97da26645ed24456f1b881e7892f..6e0a8ef5e816f3106ea14e8721aa408f41a466d2 100644 (file)
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -495,7 +495,7 @@ 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() */
@@ -516,7 +516,8 @@ 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;