[PATCH net 10/14] tcp: annotate data-races around tp->reord_seen

[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: 7ec65372ca53 ("tcp: add stat of data packet reordering events")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp.c       | 2 +-
 net/ipv4/tcp_input.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 57c4dcc8bfe948e895f713cadaad20409a9b8f14..39a4b06e36bbc63b8bc334c8f568c5a2046573b6 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4466,7 +4466,7 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
 	nla_put_u64_64bit(stats, TCP_NLA_BYTES_RETRANS,
 			  READ_ONCE(tp->bytes_retrans), TCP_NLA_PAD);
 	nla_put_u32(stats, TCP_NLA_DSACK_DUPS, READ_ONCE(tp->dsack_dups));
-	nla_put_u32(stats, TCP_NLA_REORD_SEEN, tp->reord_seen);
+	nla_put_u32(stats, TCP_NLA_REORD_SEEN, READ_ONCE(tp->reord_seen));
 	nla_put_u32(stats, TCP_NLA_SRTT, tp->srtt_us >> 3);
 	nla_put_u16(stats, TCP_NLA_TIMEOUT_REHASH, tp->timeout_rehash);
 	nla_put_u32(stats, TCP_NLA_BYTES_NOTSENT,
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 65b3ecc6be4b57f97a62d0e5737a96ddb16dd14d..896a5a5a6b1a9a678e5321dd802554ab343f7835 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1299,7 +1299,7 @@ static void tcp_check_sack_reordering(struct sock *sk, const u32 low_seq,
 	}
 
 	/* This exciting event is worth to be remembered. 8) */
-	tp->reord_seen++;
+	WRITE_ONCE(tp->reord_seen, tp->reord_seen + 1);
 	NET_INC_STATS(sock_net(sk),
 		      ts ? LINUX_MIB_TCPTSREORDER : LINUX_MIB_TCPSACKREORDER);
 }
@@ -2443,7 +2443,7 @@ static void tcp_check_reno_reordering(struct sock *sk, const int addend)
 	WRITE_ONCE(tp->reordering,
 		   min_t(u32, tp->packets_out + addend,
 			 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_max_reordering)));
-	tp->reord_seen++;
+	WRITE_ONCE(tp->reord_seen, tp->reord_seen + 1);
 	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRENOREORDER);
 }
 
-- 
2.54.0.rc1.513.gad8abe7a5a-goog