tcp: use WRITE_ONCE() for tsoffset in tcp_v6_connect()

Commit dd23c9f1e8d5 ("tcp: annotate data-races around tp->tsoffset")
updated do_tcp_getsockopt() to read tp->tsoffset with READ_ONCE()
for TCP_TIMESTAMP because another CPU may change it concurrently.

tcp_v6_connect() still stores tp->tsoffset with a plain write. That
store runs under lock_sock() via inet_stream_connect(), but the socket
lock does not serialize a concurrent getsockopt(TCP_TIMESTAMP) from
another task sharing the socket.

Use WRITE_ONCE() for the tcp_v6_connect() store so the connect-time
writer matches the lockless TCP_TIMESTAMP reader. This also makes the
IPv6 path consistent with tcp_v4_connect().

Signed-off-by: Wesley Atwell <atwellwea@gmail.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jiayuan Chen <jiayuan.chen@shopee.com>
Link: https://patch.msgid.link/20260310012604.145661-1-atwellwea@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 074b83c9a551fafa52972a41506cdaf5299e24bd..8dc3874e8b9252da60f21ad77a5ca834532e650a 100644 (file)
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -325,7 +325,7 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
                                                 inet->inet_dport);
                if (!tp->write_seq)
                        WRITE_ONCE(tp->write_seq, st.seq);
-               tp->tsoffset = st.ts_off;
+               WRITE_ONCE(tp->tsoffset, st.ts_off);
        }
 
        if (tcp_fastopen_defer_connect(sk, &err))