netdev - [PATCH net 04/11] tcp: annotate data-races around tp->keepalive

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Message-ID: <20230719212857.3943972-5-edumazet@google.com>
Date: Wed, 19 Jul 2023 21:28:50 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net 04/11] tcp: annotate data-races around tp->keepalive_intvl

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

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/tcp.h | 9 +++++++--
 net/ipv4/tcp.c    | 4 ++--
 2 files changed, 9 insertions(+), 4 deletions(-)

diff --git a/include/net/tcp.h b/include/net/tcp.h
index ff7372410472246d372402dfdfd6391544be8259..79af16a4028665d51f6ea5f1a4382265b8163309 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1507,9 +1507,14 @@ void tcp_leave_memory_pressure(struct sock *sk);
 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
 {
 	struct net *net = sock_net((struct sock *)tp);
+	int val;
+
+	/* Paired with WRITE_ONCE() in tcp_sock_set_keepintvl()
+	 * and do_tcp_setsockopt().
+	 */
+	val = READ_ONCE(tp->keepalive_intvl);
 
-	return tp->keepalive_intvl ? :
-		READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
+	return val ? : READ_ONCE(net->ipv4.sysctl_tcp_keepalive_intvl);
 }
 
 static inline int keepalive_time_when(const struct tcp_sock *tp)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index b4f7856dfb1611f02073699ee24d48f1a6fe7b87..d55fe014e7c902859243cdb619d94a230e44f708 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3345,7 +3345,7 @@ int tcp_sock_set_keepintvl(struct sock *sk, int val)
 		return -EINVAL;
 
 	lock_sock(sk);
-	tcp_sk(sk)->keepalive_intvl = val * HZ;
+	WRITE_ONCE(tcp_sk(sk)->keepalive_intvl, val * HZ);
 	release_sock(sk);
 	return 0;
 }
@@ -3559,7 +3559,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 		if (val < 1 || val > MAX_TCP_KEEPINTVL)
 			err = -EINVAL;
 		else
-			tp->keepalive_intvl = val * HZ;
+			WRITE_ONCE(tp->keepalive_intvl, val * HZ);
 		break;
 	case TCP_KEEPCNT:
 		if (val < 1 || val > MAX_TCP_KEEPCNT)
-- 
2.41.0.255.g8b1d071c50-goog