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Date:   Thu, 14 May 2020 10:02:00 +0200
From:   Daniel Borkmann <>
To:     John Fastabend <>,
Subject: Re: [bpf-next PATCH 2/3] bpf: sk_msg helpers for probe_* and

On 5/13/20 9:24 PM, John Fastabend wrote:
> Often it is useful when applying policy to know something about the
> task. If the administrator has CAP_SYS_ADMIN rights then they can
> use kprobe + sk_msg and link the two programs together to accomplish
> this. However, this is a bit clunky and also means we have to call
> sk_msg program and kprobe program when we could just use a single
> program and avoid passing metadata through sk_msg/skb, socket, etc.
> To accomplish this add probe_* helpers to sk_msg programs guarded
> by a CAP_SYS_ADMIN check. New supported helpers are the following,
>   BPF_FUNC_get_current_task
>   BPF_FUNC_current_task_under_cgroup
>   BPF_FUNC_probe_read_user
>   BPF_FUNC_probe_read_kernel
>   BPF_FUNC_probe_read
>   BPF_FUNC_probe_read_user_str
>   BPF_FUNC_probe_read_kernel_str
>   BPF_FUNC_probe_read_str

Given the current discussion in the other thread with Linus et al, please
don't add more users for BPF_FUNC_probe_read and BPF_FUNC_probe_read_str
as I'm cooking up a patch to disable them on non-x86, and cleanups from
Christoph would make them less efficient than the *_user/_kernel{,_str}()
versions anyway, so lets only add the latter.


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