linux-kernel - Re: [PATCH 2/3] perf: Use CAP_SYS_ADMIN with perf_event

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Date:   Wed, 17 Jul 2019 09:10:27 +0200
From:   Jiri Olsa <jolsa@...hat.com>
To:     "Lubashev, Igor" <ilubashe@...mai.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mathieu Poirier <mathieu.poirier@...aro.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        James Morris <jmorris@...ei.org>
Subject: Re: [PATCH 2/3] perf: Use CAP_SYS_ADMIN with perf_event_paranoid
 checks

On Tue, Jul 16, 2019 at 05:01:26PM +0000, Lubashev, Igor wrote:
> I could add another patch to the series for that.  Any suggestion for what capability to check for here?

it's:

	if (geteuid() != 0) {
		pr_err("ftrace only works for root!\n");
		return -1
	}

so I think check for CAP_SYS_ADMIN should be fine in here

jirka

> 
> (There is always an alternative to not check for anything and let the kernel refuse to perform actions that the user does not have permissions to perform.)
> 
> - Igor
> 
> -----Original Message-----
> From: Jiri Olsa <jolsa@...hat.com> 
> Sent: Tuesday, July 16, 2019 4:48 AM
> Subject: Re: [PATCH 2/3] perf: Use CAP_SYS_ADMIN with perf_event_paranoid checks
> 
> On Tue, Jul 02, 2019 at 08:10:04PM -0400, Igor Lubashev wrote:
> > The kernel is using CAP_SYS_ADMIN instead of euid==0 to override
> > perf_event_paranoid check. Make perf do the same.
> 
> I see another geteuid check in __cmd_ftrace,
> perhaps we should cover this one as well
> 
> jirka