Re: [PATCH v2 1/2] Documentation/admin-guide: introduce perf-security.rst file

Alexey Budankov
2018-11-26T08:57:28Z

Hello Jon,

On 25.11.2018 22:47, Jonathan Corbet wrote:
> On Wed, 21 Nov 2018 12:14:14 +0300
> Alexey Budankov <alexey.budankov@linux.intel.com> wrote:
>
>> +For the purpose of performing security checks Linux implementation splits
>> +processes into two categories [6]_ : a) privileged processes (whose effective
>> +user ID is 0, referred to as superuser or root), and b) unprivileged processes
>> +(whose effective UID is nonzero).
>
> Is that really what's going on here? If I understand things correctly,
> it's looking for CAP_SYS_PTRACE rather than a specific UID; am I missing
> something here?

You are right regarding CAP_SYS_PTRACE but this capability is not the only
one which is used by perf_events for security checks, so the capabilities
clarification is kept aside of these patches, because patches initial intention
is to clarify security specifics of sysctl_perf_even_paranoid settings.

I agree that the document can be extended with details clarifying capabilities
used by perf_events for security checks.

>
> (Also, you would want "*the* Linux implementation" in the first sentence
> above).

Accepted.

>
> One other thing:
>
>> +(whose effective UID is nonzero). Privileged processes bypass all kernel
>> +security permission checks so perf_events performance monitoring is fully
>> +available to privileged processes without *access*, *scope* and *resource*
>> +restrictions.
>
> Could I ask for a slight toning down of the markup here? There's a lot of
> *emphasis* here that isn't really needed and tends to get in the way.

Accepted.

Thanks,
Alexey

>
> Thanks,
>
> jon
>