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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , Willem de Bruijn , Simon Horman , Lorenz Bauer , Kuniyuki Iwashima , netdev@vger.kernel.org Subject: Re: [PATCH v1 net] net: Annotate sk->sk_write_space() for UDP SOCKMAP. In-Reply-To: <20260529193941.3897256-1-kuniyu@google.com> (Kuniyuki Iwashima's message of "Fri, 29 May 2026 19:39:23 +0000") References: <20260529193941.3897256-1-kuniyu@google.com> Date: Mon, 01 Jun 2026 12:45:05 +0200 Message-ID: <87cxya5yku.fsf@cloudflare.com> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain 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 > --- Reviewed-by: Jakub Sitnicki