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

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Message-ID: <4693ccba52114913afaafd498ae284de@ustx2ex-dag1mb5.msg.corp.akamai.com>
Date:   Wed, 17 Jul 2019 18:33:58 +0000
From:   "Lubashev, Igor" <ilubashe@...mai.com>
To:     Jiri Olsa <jolsa@...hat.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 Wednesday, July 17, 2019 3:10 AM Jiri Olsa wrote:
> 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

Thanks.  Added the [PATCH 4/3] to this series (https://lore.kernel.org/lkml/1563387359-27694-1-git-send-email-ilubashe@akamai.com/).
Let me know if you'd rather I reroll a V2 of this series.

- Igor


> 
> 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