linux-kernel - Re: [PATCH 2/5] perf: Destroy event's children on task exit

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Message-ID: <20140716121410.GA9441@krava.redhat.com>
Date:	Wed, 16 Jul 2014 14:14:10 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Jiri Olsa <jolsa@...nel.org>, linux-kernel@...r.kernel.org,
	Alexander Yarygin <yarygin@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Corey Ashford <cjashfor@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Paul Mackerras <paulus@...ba.org>
Subject: Re: [PATCH 2/5] perf: Destroy event's children on task exit

On Mon, Jul 14, 2014 at 03:35:42PM +0200, Peter Zijlstra wrote:
> On Mon, Jul 14, 2014 at 03:22:23PM +0200, Jiri Olsa wrote:
> > > > if we dont do it, the event stays installed without owner and
> > > > perf fork callback will be called and fail on permission checking
> > > > (because of owner == NULL) ... so yes, I think it's needed
> > > 
> > > Oh, right. Alternatively, we don't need permission checking for inherits
> > > at all, if we're allowed to create the initial event, we should be good
> > > for inherits.
> > 
> > I could adress that in follow up patch.. or you want this instead
> > of this one? IMO we should close those events anyway..
> 
> I tend to agree that closing them all is nicer. But we need to be
> careful while doing it so as not to make the clone/fork path block on
> it.
> 
> I _think_ it might be best to separate these two issues for the moment,
> so cure the reported problem by avoiding the permission check for
> inherited events -- IFF you agree with the previous argument that
> install_exec_creds() should be sufficient.

install_exec_creds remove removes current events any time
suid binary is executed.. so it seems ok

        /*
         * Disable monitoring for regular users
         * when executing setuid binaries. Must
         * wait until new credentials are committed
         * by commit_creds() above
         */
        if (get_dumpable(current->mm) != SUID_DUMP_USER)
                perf_event_exit_task(current);

jirka
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