netdev - Re: [PATCH v3 bpf-next 2/3] bpf: implement CAP

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Date:   Thu, 5 Sep 2019 02:51:51 +0000
From:   Song Liu <songliubraving@...com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        "David S . Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        Peter Zijlstra <peterz@...radead.org>,
        Andy Lutomirski <luto@...capital.net>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        Kernel Team <Kernel-team@...com>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>
Subject: Re: [PATCH v3 bpf-next 2/3] bpf: implement CAP_BPF



> On Sep 4, 2019, at 6:32 PM, Alexei Starovoitov <alexei.starovoitov@...il.com> wrote:
> 
> On Thu, Sep 05, 2019 at 12:34:36AM +0000, Song Liu wrote:
>> 
>> 
>>> On Sep 4, 2019, at 11:43 AM, Alexei Starovoitov <ast@...nel.org> wrote:
>>> 
>>> Implement permissions as stated in uapi/linux/capability.h
>>> 
>>> Signed-off-by: Alexei Starovoitov <ast@...nel.org>
>>> 
>> 
>> [...]
>> 
>>> @@ -1648,11 +1648,11 @@ static int bpf_prog_load(union bpf_attr *attr, union bpf_attr __user *uattr)
>>> 	is_gpl = license_is_gpl_compatible(license);
>>> 
>>> 	if (attr->insn_cnt == 0 ||
>>> -	    attr->insn_cnt > (capable(CAP_SYS_ADMIN) ? BPF_COMPLEXITY_LIMIT_INSNS : BPF_MAXINSNS))
>>> +	    attr->insn_cnt > (capable_bpf() ? BPF_COMPLEXITY_LIMIT_INSNS : BPF_MAXINSNS))
>>> 		return -E2BIG;
>>> 	if (type != BPF_PROG_TYPE_SOCKET_FILTER &&
>>> 	    type != BPF_PROG_TYPE_CGROUP_SKB &&
>>> -	    !capable(CAP_SYS_ADMIN))
>>> +	    !capable_bpf())
>>> 		return -EPERM;
>> 
>> Do we allow load BPF_PROG_TYPE_SOCKET_FILTER and BPF_PROG_TYPE_CGROUP_SKB
>> without CAP_BPF? If so, maybe highlight in the header?
> 
> of course. there is no change in behavior.
> 'highlight in the header'?
> you mean in commit log?
> I think it's a bit weird to describe things in commit that patch
> is _not_ changing vs things that patch does actually change.
> This type of comment would be great in a doc though.
> The doc will be coming separately in the follow up assuming
> the whole thing lands. I'll remember to note that bit.

I meant capability.h:

+ * CAP_BPF allows the following BPF operations:
+ * - Loading all types of BPF programs

But CAP_BPF is not required to load all types of programs. 

On a second thought, I am not sure whether we will keep capability.h
up to date with all features. So this is probably OK. 

Thanks,
Song