tcp: Fix data-races around sysctl_tcp_mtu_probing.

[ Upstream commit 4c5418176af5f7018f5292ecac0c46608234148f ]

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

Fixes: 5eb6c2893ed1 ("[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 739fc69cdcc62bf95adb169ad96d4d4b8a1d5a61..5ac81c4f076d9c82ba78adbaa4efcaf7fc927fdb 100644 (file)
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1537,7 +1537,7 @@ 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 fa2ae96ecdc407a686df0c5ffd2edf09bd17bda8..57fa707e9e980eacdb03bcd470763fe86720c264 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) {