From: Eric Dumazet <edumazet@google.com>
Date: Thu, 16 Apr 2026 20:03:08 +0000 (+0000)
Subject: tcp: add data-races annotations around tp->reordering, tp->snd_cwnd
X-Git-Tag: v7.1-rc1~36^2~60^2~11
X-Git-Url: http://git.ipfire.org/gitweb/?a=commitdiff_plain;h=829ba1f329cb7cbd56d599a6d225997fba66dc32;p=thirdparty%2Fkernel%2Flinux.git

tcp: add data-races annotations around tp->reordering, tp->snd_cwnd

tcp_get_timestamping_opt_stats() intentionally runs lockless, we must
add READ_ONCE(), WRITE_ONCE() data_race() annotations to keep KCSAN happy.

Fixes: bb7c19f96012 ("tcp: add related fields into SCM_TIMESTAMPING_OPT_STATS")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260416200319.3608680-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---

diff --git a/include/net/tcp.h b/include/net/tcp.h
index 674af493882c..ecbadcb3a744 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1513,7 +1513,7 @@ static inline u32 tcp_snd_cwnd(const struct tcp_sock *tp)
 static inline void tcp_snd_cwnd_set(struct tcp_sock *tp, u32 val)
 {
 	WARN_ON_ONCE((int)val <= 0);
-	tp->snd_cwnd = val;
+	WRITE_ONCE(tp->snd_cwnd, val);
 }
 
 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index e39e0734d958..24ba80d244b1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4445,13 +4445,13 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
 	rate64 = tcp_compute_delivery_rate(tp);
 	nla_put_u64_64bit(stats, TCP_NLA_DELIVERY_RATE, rate64, TCP_NLA_PAD);
 
-	nla_put_u32(stats, TCP_NLA_SND_CWND, tcp_snd_cwnd(tp));
-	nla_put_u32(stats, TCP_NLA_REORDERING, tp->reordering);
-	nla_put_u32(stats, TCP_NLA_MIN_RTT, tcp_min_rtt(tp));
+	nla_put_u32(stats, TCP_NLA_SND_CWND, READ_ONCE(tp->snd_cwnd));
+	nla_put_u32(stats, TCP_NLA_REORDERING, READ_ONCE(tp->reordering));
+	nla_put_u32(stats, TCP_NLA_MIN_RTT, data_race(tcp_min_rtt(tp)));
 
 	nla_put_u8(stats, TCP_NLA_RECUR_RETRANS,
 		   READ_ONCE(inet_csk(sk)->icsk_retransmits));
-	nla_put_u8(stats, TCP_NLA_DELIVERY_RATE_APP_LMT, !!tp->rate_app_limited);
+	nla_put_u8(stats, TCP_NLA_DELIVERY_RATE_APP_LMT, data_race(!!tp->rate_app_limited));
 	nla_put_u32(stats, TCP_NLA_SND_SSTHRESH, tp->snd_ssthresh);
 	nla_put_u32(stats, TCP_NLA_DELIVERED, tp->delivered);
 	nla_put_u32(stats, TCP_NLA_DELIVERED_CE, tp->delivered_ce);
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 021f745747c5..6bb6bf049a35 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1293,8 +1293,9 @@ static void tcp_check_sack_reordering(struct sock *sk, const u32 low_seq,
 			 tp->sacked_out,
 			 tp->undo_marker ? tp->undo_retrans : 0);
 #endif
-		tp->reordering = min_t(u32, (metric + mss - 1) / mss,
-				       READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering));
+		WRITE_ONCE(tp->reordering,
+			   min_t(u32, (metric + mss - 1) / mss,
+				 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering)));
 	}
 
 	/* This exciting event is worth to be remembered. 8) */
@@ -2439,8 +2440,9 @@ static void tcp_check_reno_reordering(struct sock *sk, const int addend)
 	if (!tcp_limit_reno_sacked(tp))
 		return;
 
-	tp->reordering = min_t(u32, tp->packets_out + addend,
-			       READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering));
+	WRITE_ONCE(tp->reordering,
+		   min_t(u32, tp->packets_out + addend,
+			 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering)));
 	tp->reord_seen++;
 	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRENOREORDER);
 }
@@ -2579,8 +2581,8 @@ void tcp_enter_loss(struct sock *sk)
 	reordering = READ_ONCE(net->ipv4.sysctl_tcp_reordering);
 	if (icsk->icsk_ca_state <= TCP_CA_Disorder &&
 	    tp->sacked_out >= reordering)
-		tp->reordering = min_t(unsigned int, tp->reordering,
-				       reordering);
+		WRITE_ONCE(tp->reordering,
+			   min_t(unsigned int, tp->reordering, reordering));
 
 	tcp_set_ca_state(sk, TCP_CA_Loss);
 	tp->high_seq = tp->snd_nxt;
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 06b1d5d3b6df..7a9d6d9006f6 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -496,7 +496,7 @@ void tcp_init_metrics(struct sock *sk)
 	}
 	val = tcp_metric_get(tm, TCP_METRIC_REORDERING);
 	if (val && tp->reordering != val)
-		tp->reordering = val;
+		WRITE_ONCE(tp->reordering, val);
 
 	crtt = tcp_metric_get(tm, TCP_METRIC_RTT);
 	rcu_read_unlock();