linux-kernel - Re: [PATCH net] net/netfilter: bpf: avoid leakage of skb

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Date:   Wed, 29 Nov 2023 15:47:36 +0100
From:   Florian Westphal <fw@...len.de>
To:     "D. Wythe" <alibuda@...ux.alibaba.com>
Cc:     Florian Westphal <fw@...len.de>, pablo@...filter.org,
        kadlec@...filter.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        coreteam@...filter.org, netfilter-devel@...r.kernel.org,
        davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, ast@...nel.org
Subject: Re: [PATCH net] net/netfilter: bpf: avoid leakage of skb

D. Wythe <alibuda@...ux.alibaba.com> wrote:
> And my origin intention was to allow ebpf progs to return NF_STOLEN, we are
> trying to modify some netfilter modules via ebpf,
> and some scenarios require the use of NF_STOLEN, but from your description,

NF_STOLEN can only be supported via a trusted helper, as least as far as
I understand.

Otherwise verifier would have to guarantee that any branch that returns
NF_STOLEN has released the skb, or passed it to a function that will
release the skb in the near future.