tcp: Fix data-races around keepalive sysctl knobs.

While reading sysctl_tcp_keepalive_(time|probes|intvl), they can be changed
concurrently.  Thus, we need to add READ_ONCE() to their readers.

Fixes: 1da177e ("Linux-2.6.12-rc2")
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/tcp.h

@@ -1493,21 +1493,24 @@ static inline int keepalive_intvl_when(const struct tcp_sock *tp)
 {
 	struct net *net = sock_net((struct sock *)tp);
 
-	return tp->keepalive_intvl ? : net->ipv4.sysctl_tcp_keepalive_intvl;
+	return tp->keepalive_intvl ? :
+		READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
 }
 
 static inline int keepalive_time_when(const struct tcp_sock *tp)
 {
 	struct net *net = sock_net((struct sock *)tp);
 
-	return tp->keepalive_time ? : net->ipv4.sysctl_tcp_keepalive_time;
+	return tp->keepalive_time ? :
+		READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
 }
 
 static inline int keepalive_probes(const struct tcp_sock *tp)
 {
 	struct net *net = sock_net((struct sock *)tp);
 
-	return tp->keepalive_probes ? : net->ipv4.sysctl_tcp_keepalive_probes;
+	return tp->keepalive_probes ? :
+		READ_ONCE(net->ipv4.sysctl_tcp_keepalive_probes);
 }
 
 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)

net/smc/smc_llc.c

@@ -2122,7 +2122,7 @@ void smc_llc_lgr_init(struct smc_link_group *lgr, struct smc_sock *smc)
 	init_waitqueue_head(&lgr->llc_flow_waiter);
 	init_waitqueue_head(&lgr->llc_msg_waiter);
 	mutex_init(&lgr->llc_conf_mutex);
-	lgr->llc_testlink_time = net->ipv4.sysctl_tcp_keepalive_time;
+	lgr->llc_testlink_time = READ_ONCE(net->ipv4.sysctl_tcp_keepalive_time);
 }
 
 /* called after lgr was removed from lgr_list */