linux-kernel - Re: [BUG] perf stat: events inheritance can break task targets

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Date:	Tue, 8 Jul 2014 08:59:01 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Alexander Yarygin <yarygin@...ux.vnet.ibm.com>,
	Arnaldo Carvalho de Melo <acme@...nel.com>,
	Paul Mackerras <paulus@...ba.org>,
	Ingo Molnar <mingo@...nel.org>,
	Christian Borntraeger <borntraeger@...ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [BUG] perf stat: events inheritance can break task targets

On Mon, Jul 07, 2014 at 09:46:35PM +0200, Peter Zijlstra wrote:
> On Mon, Jul 07, 2014 at 07:00:40PM +0200, Jiri Olsa wrote:
> > diff --git a/kernel/trace/trace_event_perf.c b/kernel/trace/trace_event_perf.c
> > index 5d12bb4..b44184b 100644
> > --- a/kernel/trace/trace_event_perf.c
> > +++ b/kernel/trace/trace_event_perf.c
> > @@ -24,6 +24,9 @@ static int	total_ref_count;
> >  static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
> >  				 struct perf_event *p_event)
> >  {
> > +	struct task_struct owner = p_event->parent ? p_event->parent->owner :
> > +						     p_event->owner;
> > +
> >  	if (tp_event->perf_perm) {
> >  		int ret = tp_event->perf_perm(tp_event, p_event);
> >  		if (ret)
> > @@ -32,7 +35,7 @@ static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
> >  
> >  	/* The ftrace function trace is allowed only for root. */
> >  	if (ftrace_event_is_function(tp_event)) {
> > -		if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
> > +		if (perf_paranoid_tracepoint_raw() && !has_capability(owner, CAP_SYS_ADMIN))
> >  			return -EPERM;
> >  
> >  		/*
> > @@ -65,7 +68,7 @@ static int perf_trace_event_perm(struct ftrace_event_call *tp_event,
> >  	 * ...otherwise raw tracepoint data can be a severe data leak,
> >  	 * only allow root to have these.
> >  	 */
> > -	if (perf_paranoid_tracepoint_raw() && !capable(CAP_SYS_ADMIN))
> > +	if (perf_paranoid_tracepoint_raw() && !has_capability(owner, CAP_SYS_ADMIN))
> >  		return -EPERM;
> >  
> >  	return 0;
> 
> You need to either hold rcu_read_lock() or otherwise ensure the owner is
> still valid.

ok, I'll resend

thanks,
jirka
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