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

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Message-ID: <875zgizkyk.fsf@nanos.tec.linutronix.de>
Date:   Fri, 07 Feb 2020 11:38:11 +0000
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>,
        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\@linux.intel.com" <jani.nikula@...ux.intel.com>,
        "joonas.lahtinen\@linux.intel.com" <joonas.lahtinen@...ux.intel.com>,
        "rodrigo.vivi\@intel.com" <rodrigo.vivi@...el.com>,
        "benh\@kernel.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\@vger.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        "selinux\@vger.kernel.org" <selinux@...r.kernel.org>,
        "intel-gfx\@lists.freedesktop.org" <intel-gfx@...ts.freedesktop.org>,
        "linux-parisc\@vger.kernel.org" <linux-parisc@...r.kernel.org>,
        "linuxppc-dev\@lists.ozlabs.org" <linuxppc-dev@...ts.ozlabs.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        "linux-perf-users\@vger.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

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.

Thanks,

        tglx