netdev - Re: [Patch bpf-next] unix_bpf: fix a potential deadlock in unix_dgram_bpf

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Message-ID: <CAM_iQpWGyJcx2o=HUWoyB+E-7Z1y9LEwb362TTLGxrwuz9yULg@mail.gmail.com>
Date:   Tue, 27 Jul 2021 20:06:45 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     John Fastabend <john.fastabend@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Cong Wang <cong.wang@...edance.com>,
        Eric Dumazet <eric.dumazet@...il.com>,
        Daniel Borkmann <daniel@...earbox.net>,
        Jakub Sitnicki <jakub@...udflare.com>,
        Lorenz Bauer <lmb@...udflare.com>
Subject: Re: [Patch bpf-next] unix_bpf: fix a potential deadlock in unix_dgram_bpf_recvmsg()

On Tue, Jul 27, 2021 at 9:12 AM John Fastabend <john.fastabend@...il.com> wrote:
>
> Is there a reason to grab the mutex_lock(u->iolock) above the
> skb_queue_emptyaand sk_psock_queue_empty checks?
>
> Could it be move here just above the msg_bytes_ready label?

The check of the receive queue is more accurate with lock.

Thanks.