Re: [PATCH] tcp: use WRITE_ONCE() for tsoffset in tcp_v6_connect()

[Jiayuan Chen]

On Mon, Mar 09, 2026 at 07:26:04PM +0800, Wesley Atwell wrote:
> 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@xxxxxxxxx>

I think maintainer will apply it to net-next tree after noticing Eric's comment..

Reviewed-by: Jiayuan Chen <jiayuan.chen@xxxxxxxxxx>

> ---
>  net/ipv6/tcp_ipv6.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
> index bb09d5ccf599..ba7cd7d3d4da 100644
> --- 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))