netdev - [PATCH net 06/11] tcp: annotate data-races around icsk->icsk_syn

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Message-ID: <20230719212857.3943972-7-edumazet@google.com>
Date: Wed, 19 Jul 2023 21:28:52 +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 06/11] tcp: annotate data-races around icsk->icsk_syn_retries

do_tcp_getsockopt() and reqsk_timer_handler() read
icsk->icsk_syn_retries while another cpu might change its value.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv4/inet_connection_sock.c | 2 +-
 net/ipv4/tcp.c                  | 6 +++---
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/inet_connection_sock.c b/net/ipv4/inet_connection_sock.c
index 0cc19cfbb67345960ef16bdaf6ec330a6eb397fd..aeebe881668996057d1495c84eee0f0b644b7ad0 100644
--- a/net/ipv4/inet_connection_sock.c
+++ b/net/ipv4/inet_connection_sock.c
@@ -1019,7 +1019,7 @@ static void reqsk_timer_handler(struct timer_list *t)
 
 	icsk = inet_csk(sk_listener);
 	net = sock_net(sk_listener);
-	max_syn_ack_retries = icsk->icsk_syn_retries ? :
+	max_syn_ack_retries = READ_ONCE(icsk->icsk_syn_retries) ? :
 		READ_ONCE(net->ipv4.sysctl_tcp_synack_retries);
 	/* Normally all the openreqs are young and become mature
 	 * (i.e. converted to established socket) for first timeout.
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 574fd0da167339512077c36958578fde2b1181e8..9f74ac16f1c1e53353bd14c6a04e1fa9e3de0c15 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3291,7 +3291,7 @@ int tcp_sock_set_syncnt(struct sock *sk, int val)
 		return -EINVAL;
 
 	lock_sock(sk);
-	inet_csk(sk)->icsk_syn_retries = val;
+	WRITE_ONCE(inet_csk(sk)->icsk_syn_retries, val);
 	release_sock(sk);
 	return 0;
 }
@@ -3572,7 +3572,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
 		if (val < 1 || val > MAX_TCP_SYNCNT)
 			err = -EINVAL;
 		else
-			icsk->icsk_syn_retries = val;
+			WRITE_ONCE(icsk->icsk_syn_retries, val);
 		break;
 
 	case TCP_SAVE_SYN:
@@ -3993,7 +3993,7 @@ int do_tcp_getsockopt(struct sock *sk, int level,
 		val = keepalive_probes(tp);
 		break;
 	case TCP_SYNCNT:
-		val = icsk->icsk_syn_retries ? :
+		val = READ_ONCE(icsk->icsk_syn_retries) ? :
 			READ_ONCE(net->ipv4.sysctl_tcp_syn_retries);
 		break;
 	case TCP_LINGER2:
-- 
2.41.0.255.g8b1d071c50-goog