[PATCH 5.15 68/78] tcp: annotate data-races around tp->keepalive_probes

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 6e5e1de616bf5f3df1769abc9292191dfad9110a ]

do_tcp_getsockopt() reads tp->keepalive_probes while another cpu
might change its value.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20230719212857.3943972-6-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 include/net/tcp.h | 9 +++++++--
 net/ipv4/tcp.c    | 5 +++--
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index b737ce77f7062..fe58b089f0b16 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1497,9 +1497,14 @@ static inline int keepalive_time_when(const struct tcp_sock *tp)
 static inline int keepalive_probes(const struct tcp_sock *tp)
 {
 	struct net *net = sock_net((struct sock *)tp);
+	int val;
+
+	/* Paired with WRITE_ONCE() in tcp_sock_set_keepcnt()
+	 * and do_tcp_setsockopt().
+	 */
+	val = READ_ONCE(tp->keepalive_probes);
 
-	return tp->keepalive_probes ? :
-		READ_ONCE(net->ipv4.sysctl_tcp_keepalive_probes);
+	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_probes);
 }
 
 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 8fe1098b183d0..994ac3cd50e1d 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3362,7 +3362,8 @@ int tcp_sock_set_keepcnt(struct sock *sk, int val)
 		return -EINVAL;
 
 	lock_sock(sk);
-	tcp_sk(sk)->keepalive_probes = val;
+	/* Paired with READ_ONCE() in keepalive_probes() */
+	WRITE_ONCE(tcp_sk(sk)->keepalive_probes, val);
 	release_sock(sk);
 	return 0;
 }
@@ -3570,7 +3571,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 		if (val < 1 || val > MAX_TCP_KEEPCNT)
 			err = -EINVAL;
 		else
-			tp->keepalive_probes = val;
+			WRITE_ONCE(tp->keepalive_probes, val);
 		break;
 	case TCP_SYNCNT:
 		if (val < 1 || val > MAX_TCP_SYNCNT)
-- 
2.39.2