linux-kernel - Re: [PATCH v4 bpf 1/2] bpf: fix skb_do

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Message-ID: <8c5398ac-1187-97e3-4124-30a6392e8edb@linux.dev>
Date:   Mon, 31 Jul 2023 16:52:37 -0700
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Yan Zhai <yan@...udflare.com>
Cc:     bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-kselftest@...r.kernel.org, kernel-team@...udflare.com,
        Jordan Griege <jgriege@...udflare.com>,
        Markus Elfring <Markus.Elfring@....de>,
        Jakub Sitnicki <jakub@...udflare.com>
Subject: Re: [PATCH v4 bpf 1/2] bpf: fix skb_do_redirect return values

On 7/31/23 4:01 PM, Yan Zhai wrote:
> What I commented was an exact same issue at different location: BPF
> reroute may trigger the crash as well, since it also returns
> dev_queue_xmit status in bpf_xmit. Need to fix this, or instead fixing
> LWTUNNEL_XMIT_CONTINUE value and correct the behavior at lwtunnel_xmit
> rather than bpf_xmit.

Ah. I think I got it. You meant the bpf_lwt_xmit_reroute() / BPF_LWT_REROUTE 
case? It would be clearer if some of these names were quoted instead. "reroute" 
could mean many things.

Please put details comment in v5. Thanks.

> 
> Yan
> 
>>
>>> As Dan suggested, packets might not have been freed when this is
>>> returned from drivers. The caller of dev_queue_xmit might need to free
>>> skb when this happens.
>>>
>>> Yan
>>