tcp: Fix data-races around sysctl_tcp_mtu_probing.

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

Fixes: 5d424d5a674f ("[TCP]: MTU probing")
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 11aa0ab10bbad17142b06baa7eecd7d569b33131..3fcfc0f1e9f9e7ead2c6671262e49ebcd5c7aa93 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1762,7 +1762,7 @@ void tcp_mtup_init(struct sock *sk)
        struct inet_connection_sock *icsk = inet_csk(sk);
        struct net *net = sock_net(sk);
 
-       icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1;
+       icsk->icsk_mtup.enabled = READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing) > 1;
        icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) +
                               icsk->icsk_af_ops->net_header_len;
        icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss);

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index 20cf4a98c69d85d07c884d7bc8316191ff962bd8..98bb00e29e1e9befc6ca4b8452d2bbd5c9347a7f 100644 (file)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -163,7 +163,7 @@ static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk)
        int mss;
 
        /* Black hole detection */
-       if (!net->ipv4.sysctl_tcp_mtu_probing)
+       if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing))
                return;
 
        if (!icsk->icsk_mtup.enabled) {