From: Jakub Sitnicki <jakub@cloudflare.com>
To: Kuniyuki Iwashima <kuniyu@google.com>
Cc: "David S. Miller" <davem@davemloft.net>,
Eric Dumazet <edumazet@google.com>,
Jakub Kicinski <kuba@kernel.org>,
Paolo Abeni <pabeni@redhat.com>,
Willem de Bruijn <willemb@google.com>,
Simon Horman <horms@kernel.org>,
Lorenz Bauer <lmb@cloudflare.com>,
Kuniyuki Iwashima <kuni1840@gmail.com>,
netdev@vger.kernel.org
Subject: Re: [PATCH v1 net] net: Annotate sk->sk_write_space() for UDP SOCKMAP.
Date: Mon, 01 Jun 2026 12:45:05 +0200 [thread overview]
Message-ID: <87cxya5yku.fsf@cloudflare.com> (raw)
In-Reply-To: <20260529193941.3897256-1-kuniyu@google.com> (Kuniyuki Iwashima's message of "Fri, 29 May 2026 19:39:23 +0000")
On Fri, May 29, 2026 at 07:39 PM GMT, Kuniyuki Iwashima wrote:
> UDP TX skb->destructor() is sock_wfree(), and UDP holds lock_sock()
> only for UDP_CORK / MSG_MORE sendmsg().
Nit: lock_sock() serializes map updates via bpf() syscall. We also have
sockmap iterator programs which can insert UDP sockets into sockmap. On
this path, sock_map_update_elem, we grab only bh_lock_sock, so the race
against UDP_CORK / MSG_MORE sendmsg() path also exists.
> Otherwise, sk->sk_write_space() may be read locklessly while SOCKMAP
> rewrites sk->sk_write_space().
>
> Let's use WRITE_ONCE() and READ_ONCE() for sk->sk_write_space().
>
> Note that the write side is annotated by commit 2ef2b20cf4e0
> ("net: annotate data-races around sk->sk_{data_ready,write_space}").
>
> Fixes: 7b98cd42b049 ("bpf: sockmap: Add UDP support")
> Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
> ---
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
next prev parent reply other threads:[~2026-06-01 10:45 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-05-29 19:39 [PATCH v1 net] net: Annotate sk->sk_write_space() for UDP SOCKMAP Kuniyuki Iwashima
2026-06-01 10:45 ` Jakub Sitnicki [this message]
2026-06-02 19:00 ` patchwork-bot+netdevbpf
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