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

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On 11/29/23 10:47 PM, Florian Westphal wrote:
D. Wythe <alibuda@xxxxxxxxxxxxxxxxx> 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.

Thank you very much for your help. I now understand the difficulty here.
The verifier cannot determine whether the consume_skb() was executed or not,
when the return value  goes to NF_STOLEN.

We may use NF_DROP at first, it won't be make much difference for us now.

Also, do you have any plans to support this helper?

Best wishes,
D. Wythe

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