linux-kernel - Re: [PATCH bpf] bpf: fix recursive lock when verdict program return SK

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Message-ID: <2939664d-e38d-4ac4-b8cf-3ef60c5fd5c6@linux.dev>
Date: Fri, 8 Nov 2024 13:03:45 -0800
From: Martin KaFai Lau <martin.lau@...ux.dev>
To: mrpre <mrpre@....com>, John Fastabend <john.fastabend@...il.com>,
 Jakub Sitnicki <jakub@...udflare.com>
Cc: edumazet@...gle.com, jakub@...udflare.com, davem@...emloft.net,
 dsahern@...nel.org, kuba@...nel.org, pabeni@...hat.com,
 netdev@...r.kernel.org, bpf@...r.kernel.orgc, linux-kernel@...r.kernel.org,
 Vincent Whitchurch <vincent.whitchurch@...adoghq.com>
Subject: Re: [PATCH bpf] bpf: fix recursive lock when verdict program return
 SK_PASS

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@...adoghq.com>
> Signed-off-by: Jiayuan Chen <mrpre@....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@...il.com>

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