[PATCH net 02/14] tcp: add data-race annotations around tp->data_segs_out and tp->total_retrans

[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: 7e98102f4897 ("tcp: record pkts sent and retransmistted")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp.c        | 4 ++--
 net/ipv4/tcp_output.c | 8 +++++---
 2 files changed, 7 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 7b7812cb710f6e05a83615811eefd0cf8a845cab..e39e0734d958f39aa83a33f5c608ce3b94232fb1 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4434,9 +4434,9 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
 	nla_put_u64_64bit(stats, TCP_NLA_SNDBUF_LIMITED,
 			  info.tcpi_sndbuf_limited, TCP_NLA_PAD);
 	nla_put_u64_64bit(stats, TCP_NLA_DATA_SEGS_OUT,
-			  tp->data_segs_out, TCP_NLA_PAD);
+			  READ_ONCE(tp->data_segs_out), TCP_NLA_PAD);
 	nla_put_u64_64bit(stats, TCP_NLA_TOTAL_RETRANS,
-			  tp->total_retrans, TCP_NLA_PAD);
+			  READ_ONCE(tp->total_retrans), TCP_NLA_PAD);
 
 	rate = READ_ONCE(sk->sk_pacing_rate);
 	rate64 = (rate != ~0UL) ? rate : ~0ULL;
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 8e99687526a64cef0c8f7b8f0d5ec7a5fa883f09..d8e8bba2d03a3be5e7a9ebac16e39f4a29ae6037 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1688,7 +1688,8 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
 
 	if (skb->len != tcp_header_size) {
 		tcp_event_data_sent(tp, sk);
-		tp->data_segs_out += tcp_skb_pcount(skb);
+		WRITE_ONCE(tp->data_segs_out,
+			   tp->data_segs_out + tcp_skb_pcount(skb));
 		tp->bytes_sent += skb->len - tcp_header_size;
 	}
 
@@ -3642,7 +3643,7 @@ int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs)
 	TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs);
 	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)
 		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
-	tp->total_retrans += segs;
+	WRITE_ONCE(tp->total_retrans, tp->total_retrans + segs);
 	tp->bytes_retrans += skb->len;
 
 	/* make sure skb->data is aligned on arches that require it
@@ -4646,7 +4647,8 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
 			 * However in this case, we are dealing with a passive fastopen
 			 * socket thus we can change total_retrans value.
 			 */
-			tcp_sk_rw(sk)->total_retrans++;
+			WRITE_ONCE(tcp_sk_rw(sk)->total_retrans,
+				   tcp_sk_rw(sk)->total_retrans + 1);
 		}
 		trace_tcp_retransmit_synack(sk, req);
 		WRITE_ONCE(req->num_retrans, req->num_retrans + 1);
-- 
2.54.0.rc1.513.gad8abe7a5a-goog