netdev - Re: [PATCH bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf

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Date:   Wed, 26 Jun 2019 15:19:00 +0000
From:   Song Liu <songliubraving@...com>
To:     Lorenz Bauer <lmb@...udflare.com>
CC:     Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        "Alexei Starovoitov" <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Kernel Team <Kernel-team@...com>
Subject: Re: [PATCH bpf-next 1/4] bpf: unprivileged BPF access via /dev/bpf



> On Jun 26, 2019, at 6:45 AM, Lorenz Bauer <lmb@...udflare.com> wrote:
> 
> On Tue, 25 Jun 2019 at 19:23, Song Liu <songliubraving@...com> wrote:
>> 
>> This patch introduce unprivileged BPF access. The access control is
>> achieved via device /dev/bpf. Users with access to /dev/bpf are able
>> to access BPF syscall.
>> 
>> Two ioctl command are added to /dev/bpf:
>> 
>> The first two commands get/put permission to access sys_bpf. This
>> permission is noted by setting bit TASK_BPF_FLAG_PERMITTED of
>> current->bpf_flags. This permission cannot be inherited via fork().
> 
> I know nothing about the scheduler, so pardon my ignorance. Does
> TASK_BPF_FLAG_PERMITTED apply per user-space process, or per thread?

It is per thread. clone() also clears the bit. I will make it more
clear int the commit log. 

Thanks,
Song