[PATCH net 06/14] tcp: add data-race annotations for TCP_NLA_SNDQ_SIZE

[Eric Dumazet <edumazet@google.com>]

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

Fixes: 87ecc95d81d9 ("tcp: add send queue size stat in SCM_TIMESTAMPING_OPT_STATS")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp.c        | 4 +++-
 net/ipv4/tcp_input.c  | 4 ++--
 net/ipv4/tcp_output.c | 2 +-
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 0aabd02d44967dae3e569702f76037beb45e5de8..729936d13a5c6d9c39edc880636e01cf0973688e 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4456,7 +4456,9 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
 	nla_put_u32(stats, TCP_NLA_DELIVERED, READ_ONCE(tp->delivered));
 	nla_put_u32(stats, TCP_NLA_DELIVERED_CE, READ_ONCE(tp->delivered_ce));
 
-	nla_put_u32(stats, TCP_NLA_SNDQ_SIZE, tp->write_seq - tp->snd_una);
+	nla_put_u32(stats, TCP_NLA_SNDQ_SIZE,
+		    max_t(int, 0,
+			  READ_ONCE(tp->write_seq) - READ_ONCE(tp->snd_una)));
 	nla_put_u8(stats, TCP_NLA_CA_STATE, inet_csk(sk)->icsk_ca_state);
 
 	nla_put_u64_64bit(stats, TCP_NLA_BYTES_SENT, tp->bytes_sent,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 63ff89210a72fbf5710279c41010d3f6e734e522..edb5013873e0c4a9ba2f8a81a43eff5fb6e7a47b 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3912,7 +3912,7 @@ static void tcp_snd_una_update(struct tcp_sock *tp, u32 ack)
 	sock_owned_by_me((struct sock *)tp);
 	tp->bytes_acked += delta;
 	tcp_snd_sne_update(tp, ack);
-	tp->snd_una = ack;
+	WRITE_ONCE(tp->snd_una, ack);
 }
 
 static void tcp_rcv_sne_update(struct tcp_sock *tp, u32 seq)
@@ -7240,7 +7240,7 @@ tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 		if (sk->sk_socket)
 			sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT);
 
-		tp->snd_una = TCP_SKB_CB(skb)->ack_seq;
+		WRITE_ONCE(tp->snd_una, TCP_SKB_CB(skb)->ack_seq);
 		tp->snd_wnd = ntohs(th->window) << tp->rx_opt.snd_wscale;
 		tcp_init_wl(tp, TCP_SKB_CB(skb)->seq);
 
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 2663505a0dd7a0eae69f6a91250b4a0b6f357f7d..9f83c7e4acabc64f0a45e4879c326694a306b368 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4153,7 +4153,7 @@ static void tcp_connect_init(struct sock *sk)
 	tp->snd_wnd = 0;
 	tcp_init_wl(tp, 0);
 	tcp_write_queue_purge(sk);
-	tp->snd_una = tp->write_seq;
+	WRITE_ONCE(tp->snd_una, tp->write_seq);
 	tp->snd_sml = tp->write_seq;
 	tp->snd_up = tp->write_seq;
 	WRITE_ONCE(tp->snd_nxt, tp->write_seq);
-- 
2.54.0.rc1.513.gad8abe7a5a-goog