linux-kernel - Re: [PATCH] perf tools: Fixup for removing -f option in perf record

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Date:	Fri, 28 Jun 2013 18:07:11 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	David Ahern <dsahern@...il.com>
Cc:	Jiri Olsa <jolsa@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
	Paul Mackerras <paulus@...ba.org>,
	Namhyung Kim <namhyung.kim@....com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf tools: Fixup for removing -f option in perf record


* David Ahern <dsahern@...il.com> wrote:

> On 6/28/13 9:37 AM, Ingo Molnar wrote:
> >
> >* David Ahern <dsahern@...il.com> wrote:
> >
> >>On 6/28/13 3:47 AM, Jiri Olsa wrote:
> >>>>>I thought -f was the implied default for ages?
> >>>>
> >>>>OK.. I've been dutifully typing it all this while :-)
> >>>
> >>>The '-f' option in record command had no affect.. myabe it got
> >>>depreceated when we started to backup perf.data to perf.data.old..?
> >>
> >>Way back in 2010, 2.6.34 kernel - 7865e817 commit. I've been typing
> >>the -f for while too. Now about the need for the pesky -f on the
> >>analysis side....
> >
> >That's only needed when perf.data is owned by a different user, right?
> >
> 
> Yes, why not let file permissions dictate of uid x can read uid y files? 
> Why does perf need to have that restriction? For example, QA collects 
> the data files, developers analyze them.

So, the thinking behind that is that user should not be able to
generate a malicious perf.data file and let root (or another user)
run it accidentally.

( That presumes some sort of exploitable parsing bug or other buffer 
  overflow in perf. )

I don't feel terribly strongly about it though.

Thanks,

	Ingo
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