[PATCH 5.10 056/105] tcp: Fix data-races around sysctl_tcp_fastopen_blackhole_timeout.

[Greg Kroah-Hartman]

From: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>

[ Upstream commit 021266ec640c7a4527e6cd4b7349a512b351de1d ]

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

Fixes: cf1ef3f0719b ("net/tcp_fastopen: Disable active side TFO in certain scenarios")
Signed-off-by: Kuniyuki Iwashima <kuniyu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
 net/ipv4/tcp_fastopen.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp_fastopen.c b/net/ipv4/tcp_fastopen.c
index ed7aa6ae7b51..39fb037ce5f3 100644
--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -506,7 +506,7 @@ void tcp_fastopen_active_disable(struct sock *sk)
 {
 	struct net *net = sock_net(sk);
 
-	if (!sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout)
+	if (!READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout))
 		return;
 
 	/* Paired with READ_ONCE() in tcp_fastopen_active_should_disable() */
@@ -527,7 +527,8 @@ void tcp_fastopen_active_disable(struct sock *sk)
  */
 bool tcp_fastopen_active_should_disable(struct sock *sk)
 {
-	unsigned int tfo_bh_timeout = sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout;
+	unsigned int tfo_bh_timeout =
+		READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_fastopen_blackhole_timeout);
 	unsigned long timeout;
 	int tfo_da_times;
 	int multiplier;
-- 
2.35.1