Commit ab1ba21b authored by Kuniyuki Iwashima's avatar Kuniyuki Iwashima Committed by David S. Miller
Browse files

tcp: Fix data-races around sysctl_tcp_no_ssthresh_metrics_save. 



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

Fixes: 65e6d901 ("net-tcp: Disable TCP ssthresh metrics cache by default")
Signed-off-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8499a245

net/ipv4/tcp_metrics.c

+4 −4
Original line number Diff line number Diff line
@@ -385,7 +385,7 @@ void tcp_update_metrics(struct sock *sk) 


	if (tcp_in_initial_slowstart(tp)) {

		/* Slow start still did not finish. */

		if (!net->ipv4.sysctl_tcp_no_ssthresh_metrics_save &&

		if (!READ_ONCE(net->ipv4.sysctl_tcp_no_ssthresh_metrics_save) &&

		    !tcp_metric_locked(tm, TCP_METRIC_SSTHRESH)) {

			val = tcp_metric_get(tm, TCP_METRIC_SSTHRESH);

			if (val && (tcp_snd_cwnd(tp) >> 1) > val)
@@ -401,7 +401,7 @@ void tcp_update_metrics(struct sock *sk) 
	} else if (!tcp_in_slow_start(tp) &&

		   icsk->icsk_ca_state == TCP_CA_Open) {

		/* Cong. avoidance phase, cwnd is reliable. */

		if (!net->ipv4.sysctl_tcp_no_ssthresh_metrics_save &&

		if (!READ_ONCE(net->ipv4.sysctl_tcp_no_ssthresh_metrics_save) &&

		    !tcp_metric_locked(tm, TCP_METRIC_SSTHRESH))

			tcp_metric_set(tm, TCP_METRIC_SSTHRESH,

				       max(tcp_snd_cwnd(tp) >> 1, tp->snd_ssthresh));
@@ -418,7 +418,7 @@ void tcp_update_metrics(struct sock *sk) 
			tcp_metric_set(tm, TCP_METRIC_CWND,

				       (val + tp->snd_ssthresh) >> 1);

		}

		if (!net->ipv4.sysctl_tcp_no_ssthresh_metrics_save &&

		if (!READ_ONCE(net->ipv4.sysctl_tcp_no_ssthresh_metrics_save) &&

		    !tcp_metric_locked(tm, TCP_METRIC_SSTHRESH)) {

			val = tcp_metric_get(tm, TCP_METRIC_SSTHRESH);

			if (val && tp->snd_ssthresh > val)
@@ -463,7 +463,7 @@ void tcp_init_metrics(struct sock *sk) 
	if (tcp_metric_locked(tm, TCP_METRIC_CWND))

		tp->snd_cwnd_clamp = tcp_metric_get(tm, TCP_METRIC_CWND);



	val = net->ipv4.sysctl_tcp_no_ssthresh_metrics_save ?

	val = READ_ONCE(net->ipv4.sysctl_tcp_no_ssthresh_metrics_save) ?

	      0 : tcp_metric_get(tm, TCP_METRIC_SSTHRESH);

	if (val) {

		tp->snd_ssthresh = val;