linux-kernel - Re: [PATCH v2] perf_event_open.2: update the man page with CAP

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Message-ID: <CAKgNAkhSXG88D6qHYzXskOL0XDDatQT3sX0L-AnUwz9fqa8pNg@mail.gmail.com>
Date:   Tue, 27 Oct 2020 18:11:34 +0100
From:   "Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:     Alexey Budankov <alexey.budankov@...ux.intel.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andi Kleen <ak@...ux.intel.com>,
        linux-man <linux-man@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] perf_event_open.2: update the man page with
 CAP_PERFMON related information

On Tue, 27 Oct 2020 at 18:10, Alexey Budankov
<alexey.budankov@...ux.intel.com> wrote:
>
>
> On 27.10.2020 19:57, Michael Kerrisk (man-pages) wrote:
> > Hello Alexey,
> >
> > On 10/27/20 5:48 PM, Alexey Budankov wrote:
> >>
> >> Extend perf_event_open 2 man page with the information about
> >> CAP_PERFMON capability designed to secure performance monitoring
> >> and observability operation in a system according to the principle
> >> of least privilege [1] (POSIX IEEE 1003.1e, 2.2.2.39).
> >>
> >> [1] https://sites.google.com/site/fullycapable/, posix_1003.1e-990310.pdf
> >>
> >> Signed-off-by: Alexey Budankov <alexey.budankov@...ux.intel.com>
> >
> > Thanks for this. I've applied. I have a few questions/comments below.
> >
> >> ---
> >>  man2/perf_event_open.2 | 32 ++++++++++++++++++++++++++++++--
> >>  1 file changed, 30 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2
> >> index 4827a359d..9810bc554 100644
> >> --- a/man2/perf_event_open.2
> >> +++ b/man2/perf_event_open.2
> >> @@ -97,6 +97,8 @@ when running on the specified CPU.
> >>  .BR "pid == \-1" " and " "cpu >= 0"
> >>  This measures all processes/threads on the specified CPU.
> >>  This requires
> >> +.B CAP_PERFMON
> >> +(since Linux 5.8) or
> >>  .B CAP_SYS_ADMIN
> >>  capability or a
> >>  .I /proc/sys/kernel/perf_event_paranoid
> >> @@ -108,9 +110,11 @@ This setting is invalid and will return an error.
> >>  When
> >>  .I pid
> >>  is greater than zero, permission to perform this system call
> >> -is governed by a ptrace access mode
> >> +is governed by
> >> +.B CAP_PERFMON
> >> +(since Linux 5.9) and a ptrace access mode
> >
> > I want to check: did you really mean 5.9 here? (Everywhere else,
> > 5.8 is mentioned, but perhaps this change came in the next kernel
> > version.)
>
> Yes, it is not a typo. This thing was merged into v5.9.
>
> Thanks,
> Alexei

Thanks, Alexei!



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/