tcp: Fix data-races around sysctl_tcp_mtu_probing.

[ Upstream commit f47d00e077e7d61baf69e46dde3210c886360207 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8634a5c853f513e038c4a2b116c74cbbaa64eca1..423ec09ad83167d814824b468c4cca2623a2e330 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1763,7 +1763,7 @@ 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 4ef08079ccfa9d0e68f046b3cb329e7e3efdf1ff..3c0d689cafaca0b5e054942d6d6395bf73e7bf34 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) {