tcp: annotate data-races around (tp->write_seq - tp->snd_nxt)

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

WRITE_ONCE() annotations are already present.

Fixes: e08ab0b377a1 ("tcp: add bytes not sent to SCM_TIMESTAMPING_OPT_STATS")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260416200319.3608680-14-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 192e95b71ce9868980a809184be83398d8740427..68894c03f2622d1a08fd747ff4c5e32be8579d2c 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4472,7 +4472,8 @@ struct sk_buff *tcp_get_timestamping_opt_stats(const struct sock *sk,
        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));
+                   max_t(int, 0,
+                         READ_ONCE(tp->write_seq) - READ_ONCE(tp->snd_nxt)));
        nla_put_u64_64bit(stats, TCP_NLA_EDT, orig_skb->skb_mstamp_ns,
                          TCP_NLA_PAD);
        if (ack_skb)