Re: [PATCH bpf] bpf: fix recursive lock when verdict program return SK_PASS

[Martin KaFai Lau <martin.lau@linux.dev>]

On 11/6/24 4:44 AM, mrpre wrote:
> When the stream_verdict program returns SK_PASS, it places the received skb
> into its own receive queue, but a recursive lock eventually occurs, leading
> to an operating system deadlock. This issue has been present since v6.9.
> 
> '''
> sk_psock_strp_data_ready
>      write_lock_bh(&sk->sk_callback_lock)
>      strp_data_ready
>        strp_read_sock
>          read_sock -> tcp_read_sock
>            strp_recv
>              cb.rcv_msg -> sk_psock_strp_read
>                # now stream_verdict return SK_PASS without peer sock assign
>                __SK_PASS = sk_psock_map_verd(SK_PASS, NULL)
>                sk_psock_verdict_apply
>                  sk_psock_skb_ingress_self
>                    sk_psock_skb_ingress_enqueue
>                      sk_psock_data_ready
>                        read_lock_bh(&sk->sk_callback_lock) <= dead lock
> 
> '''
> 
> This topic has been discussed before, but it has not been fixed.
> Previous discussion:
> https://lore.kernel.org/all/6684a5864ec86_403d20898@john.notmuch

Is the selftest included in this link still useful to reproduce this bug?
If yes, please include that also.

> 
> Fixes: 6648e613226e ("bpf, skmsg: Fix NULL pointer dereference in sk_psock_skb_ingress_enqueue")
> Reported-by: Vincent Whitchurch <vincent.whitchurch@datadoghq.com>
> Signed-off-by: Jiayuan Chen <mrpre@163.com>

Please also use the real name in the author (i.e. the email sender). The patch 
needs a real author name also. I had manually fixed one of your earlier 
lock_sock fix before applying.

pw-bot: cr

> Signed-off-by: John Fastabend <john.fastabend@gmail.com>

The patch and the earlier discussion make sense to me.
John and JakubS, please help to take another look in the next respin.