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

[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: 29c1c44646ae ("tcp: add u32 counter in tcp_sock and an SNMP counter for PLB")
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp.c     | 3 ++-
 net/ipv4/tcp_plb.c | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 68894c03f2622d1a08fd747ff4c5e32be8579d2c..7fbf2fca5eb2c63763231d4d55b770b85a7cbdbf 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4480,7 +4480,8 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
 		nla_put_u8(stats, TCP_NLA_TTL,
 			   tcp_skb_ttl_or_hop_limit(ack_skb));
 
-	nla_put_u32(stats, TCP_NLA_REHASH, tp->plb_rehash + tp->timeout_rehash);
+	nla_put_u32(stats, TCP_NLA_REHASH,
+		    READ_ONCE(tp->plb_rehash) + READ_ONCE(tp->timeout_rehash));
 	return stats;
 }
 
diff --git a/net/ipv4/tcp_plb.c b/net/ipv4/tcp_plb.c
index 68ccdb9a54127632b6b764b5cbb18e1589ab1aa7..c11a0cd3f8feb004150a4056f5ca57f90d2cb2b8 100644
--- a/net/ipv4/tcp_plb.c
+++ b/net/ipv4/tcp_plb.c
@@ -80,7 +80,7 @@ void tcp_plb_check_rehash(struct sock *sk, struct tcp_plb_state *plb)
 
 	sk_rethink_txhash(sk);
 	plb->consec_cong_rounds = 0;
-	tcp_sk(sk)->plb_rehash++;
+	WRITE_ONCE(tcp_sk(sk)->plb_rehash, tcp_sk(sk)->plb_rehash + 1);
 	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPPLBREHASH);
 }
 EXPORT_SYMBOL_GPL(tcp_plb_check_rehash);
-- 
2.54.0.rc1.513.gad8abe7a5a-goog