tcp: annotate data-races around tp->timeout_rehash

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

Fixes: 32efcc06d2a1 ("tcp: export count for rehash attempts")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260416200319.3608680-13-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 541bd0d2d8c4ed24934fd047dd46e532b30021be..192e95b71ce9868980a809184be83398d8740427 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4469,7 +4469,8 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
        nla_put_u32(stats, TCP_NLA_DSACK_DUPS, READ_ONCE(tp->dsack_dups));
        nla_put_u32(stats, TCP_NLA_REORD_SEEN, READ_ONCE(tp->reord_seen));
        nla_put_u32(stats, TCP_NLA_SRTT, READ_ONCE(tp->srtt_us) >> 3);
-       nla_put_u16(stats, TCP_NLA_TIMEOUT_REHASH, tp->timeout_rehash);
+       nla_put_u16(stats, TCP_NLA_TIMEOUT_REHASH,
+                   READ_ONCE(tp->timeout_rehash));
        nla_put_u32(stats, TCP_NLA_BYTES_NOTSENT,
                    max_t(int, 0, tp->write_seq - tp->snd_nxt));
        nla_put_u64_64bit(stats, TCP_NLA_EDT, orig_skb->skb_mstamp_ns,

diff --git a/net/ipv4/tcp_timer.c b/net/ipv4/tcp_timer.c
index ea99988795e7e87412eef2768c4471e90c3e873e..8d791a954cd6ced52380226f205c66224b8f8bbd 100644 (file)
--- a/net/ipv4/tcp_timer.c
+++ b/net/ipv4/tcp_timer.c
@@ -297,7 +297,7 @@ static int tcp_write_timeout(struct sock *sk)
        }
 
        if (sk_rethink_txhash(sk)) {
-               tp->timeout_rehash++;
+               WRITE_ONCE(tp->timeout_rehash, tp->timeout_rehash + 1);
                __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH);
        }