linux-kernel - Re: [PATCH v5 01/10] capabilities: introduce CAP

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Message-ID: <95aa57e6-4d78-39df-386c-a98734f19777@linux.intel.com>
Date:   Thu, 20 Feb 2020 16:05:11 +0300
From:   Alexey Budankov <alexey.budankov@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Stephen Smalley <sds@...ho.nsa.gov>,
        Serge Hallyn <serge@...lyn.com>,
        James Morris <jmorris@...ei.org>
Cc:     Alexei Starovoitov <alexei.starovoitov@...il.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        "jani.nikula@...ux.intel.com" <jani.nikula@...ux.intel.com>,
        "joonas.lahtinen@...ux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        "rodrigo.vivi@...el.com" <rodrigo.vivi@...el.com>,
        "benh@...nel.crashing.org" <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Will Deacon <will.deacon@....com>,
        Mark Rutland <mark.rutland@....com>,
        Robert Richter <rric@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>, Andi Kleen <ak@...ux.intel.com>,
        Stephane Eranian <eranian@...gle.com>,
        Igor Lubashev <ilubashe@...mai.com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Song Liu <songliubraving@...com>,
        Lionel Landwerlin <lionel.g.landwerlin@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "selinux@...r.kernel.org" <selinux@...r.kernel.org>,
        "intel-gfx@...ts.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>,
        "linuxppc-dev@...ts.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-perf-users@...r.kernel.org" <linux-perf-users@...r.kernel.org>,
        oprofile-list@...ts.sf.net, Andy Lutomirski <luto@...capital.net>
Subject: Re: [PATCH v5 01/10] capabilities: introduce CAP_PERFMON to kernel
 and user space


On 07.02.2020 16:39, Alexey Budankov wrote:
> 
> On 07.02.2020 14:38, Thomas Gleixner wrote:
>> Alexey Budankov <alexey.budankov@...ux.intel.com> writes:
>>> On 22.01.2020 17:25, Alexey Budankov wrote:
>>>> On 22.01.2020 17:07, Stephen Smalley wrote:
>>>>>> It keeps the implementation simple and readable. The implementation is more
>>>>>> performant in the sense of calling the API - one capable() call for CAP_PERFMON
>>>>>> privileged process.
>>>>>>
>>>>>> Yes, it bloats audit log for CAP_SYS_ADMIN privileged and unprivileged processes,
>>>>>> but this bloating also advertises and leverages using more secure CAP_PERFMON
>>>>>> based approach to use perf_event_open system call.
>>>>>
>>>>> I can live with that.  We just need to document that when you see
>>>>> both a CAP_PERFMON and a CAP_SYS_ADMIN audit message for a process,
>>>>> try only allowing CAP_PERFMON first and see if that resolves the
>>>>> issue.  We have a similar issue with CAP_DAC_READ_SEARCH versus
>>>>> CAP_DAC_OVERRIDE.
>>>>
>>>> perf security [1] document can be updated, at least, to align and document 
>>>> this audit logging specifics.
>>>
>>> And I plan to update the document right after this patch set is accepted.
>>> Feel free to let me know of the places in the kernel docs that also
>>> require update w.r.t CAP_PERFMON extension.
>>
>> The documentation update wants be part of the patch set and not planned
>> to be done _after_ the patch set is merged.
> 
> Well, accepted. It is going to make patches #11 and beyond.

Patches #11 and #12 of v7 [1] contain information on CAP_PERFMON intention and usage.
Patch for man-pages [2] extends perf_event_open.2 documentation.

Thanks,
Alexey

---
[1] https://lore.kernel.org/lkml/c8de937a-0b3a-7147-f5ef-69f467e87a13@linux.intel.com/
[2] https://lore.kernel.org/lkml/18d1083d-efe5-f5f8-c531-d142c0e5c1a8@linux.intel.com/