From: Kuniyuki Iwashima <kuniyu@amazon.com>
To: <edumazet@google.com>
Cc: <davem@davemloft.net>, <eric.dumazet@gmail.com>,
<kuba@kernel.org>, <kuniyu@amazon.com>, <netdev@vger.kernel.org>,
<pabeni@redhat.com>, <willemb@google.com>
Subject: [PATCH net] af_packet: do not use READ_ONCE() in packet_bind()
Date: Fri, 26 May 2023 09:23:20 -0700 [thread overview]
Message-ID: <20230526162320.5816-1-kuniyu@amazon.com> (raw)
In-Reply-To: <20230526154342.2533026-1-edumazet@google.com>
From: Eric Dumazet <edumazet@google.com>
Date: Fri, 26 May 2023 15:43:42 +0000
> A recent patch added READ_ONCE() in packet_bind() and packet_bind_spkt()
>
> This is better handled by reading pkt_sk(sk)->num later
> in packet_do_bind() while appropriate lock is held.
>
> READ_ONCE() in writers are often an evidence of something being wrong.
>
> Fixes: 822b5a1c17df ("af_packet: Fix data-races of pkt_sk(sk)->num.")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Cc: Kuniyuki Iwashima <kuniyu@amazon.com>
> Cc: Willem de Bruijn <willemb@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Thanks!
> ---
> net/packet/af_packet.c | 8 +++++---
> 1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
> index a1f9a0e9f3c8a72e5a95f96473b7b6c63f893935..a2dbeb264f260e5b8923ece9aac99fe19ddfeb62 100644
> --- a/net/packet/af_packet.c
> +++ b/net/packet/af_packet.c
> @@ -3201,6 +3201,9 @@ static int packet_do_bind(struct sock *sk, const char *name, int ifindex,
>
> lock_sock(sk);
> spin_lock(&po->bind_lock);
> + if (!proto)
> + proto = po->num;
> +
> rcu_read_lock();
>
> if (po->fanout) {
> @@ -3299,7 +3302,7 @@ static int packet_bind_spkt(struct socket *sock, struct sockaddr *uaddr,
> memcpy(name, uaddr->sa_data, sizeof(uaddr->sa_data_min));
> name[sizeof(uaddr->sa_data_min)] = 0;
>
> - return packet_do_bind(sk, name, 0, READ_ONCE(pkt_sk(sk)->num));
> + return packet_do_bind(sk, name, 0, 0);
> }
>
> static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
> @@ -3316,8 +3319,7 @@ static int packet_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len
> if (sll->sll_family != AF_PACKET)
> return -EINVAL;
>
> - return packet_do_bind(sk, NULL, sll->sll_ifindex,
> - sll->sll_protocol ? : READ_ONCE(pkt_sk(sk)->num));
> + return packet_do_bind(sk, NULL, sll->sll_ifindex, sll->sll_protocol);
> }
>
> static struct proto packet_proto = {
> --
> 2.41.0.rc0.172.g3f132b7071-goog
next prev parent reply other threads:[~2023-05-26 16:23 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-26 15:43 [PATCH net] af_packet: do not use READ_ONCE() in packet_bind() Eric Dumazet
2023-05-26 16:09 ` Willem de Bruijn
2023-05-26 16:14 ` Jiri Pirko
2023-05-26 16:23 ` Kuniyuki Iwashima [this message]
2023-05-30 5:20 ` patchwork-bot+netdevbpf
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