Re: perf,ftrace: fuzzer triggers warning in trace_events_filter code

[Steven Rostedt <rostedt@goodmis.org>]

On Mon, 15 Jun 2015 17:50:25 -0400
Steven Rostedt <rostedt@goodmis.org> wrote:

> On Fri, 12 Jun 2015 21:15:10 -0400 (EDT)
> Vince Weaver <vincent.weaver@maine.edu> wrote:
> 
> > On Fri, 12 Jun 2015, Steven Rostedt wrote:
> > 
> > > On Fri, 12 Jun 2015 17:18:22 -0400 (EDT)
> > > Vince Weaver <vincent.weaver@maine.edu> wrote:
> > > 
> > > > 
> > > > So I've modified my fuzzer to try to exercise the 
> > > > PERF_EVENT_IOC_SET_FILTER ioctl() and it is starting to turn up some 
> > > > warnings.
> > > 
> > > Is there any way to know what the filter string you used that generated
> > > this?
> > 
> > Various seem to trigger it.  One example is
> > 
> > 	ext4:ext4_truncate_exit
> > 	(((dev<=913)blocks==916)common_type&756)
> > 
> 
> Does this patch fix your issue?

I got this patch all ready and set to push to Linus. But I was hoping
to add a Tested-by: from you. I already have you as Reported-by.

I would like to get this in before 4.1 is released.

Thanks,

-- Steve

> 
> diff --git a/kernel/trace/trace_events_filter.c b/kernel/trace/trace_events_filter.c
> index 71511ebc70db..dae84db83d97 100644
> --- a/kernel/trace/trace_events_filter.c
> +++ b/kernel/trace/trace_events_filter.c
> @@ -1369,19 +1369,26 @@ static int check_preds(struct filter_parse_state *ps)
>  {
>  	int n_normal_preds = 0, n_logical_preds = 0;
>  	struct postfix_elt *elt;
> +	int cnt = 0;
>  
>  	list_for_each_entry(elt, &ps->postfix, list) {
> -		if (elt->op == OP_NONE)
> +		if (elt->op == OP_NONE) {
> +			cnt++;
>  			continue;
> +		}
>  
>  		if (elt->op == OP_AND || elt->op == OP_OR) {
>  			n_logical_preds++;
> +			cnt--;
>  			continue;
>  		}
> +		if (elt->op != OP_NOT)
> +			cnt--;
>  		n_normal_preds++;
> +		WARN_ON_ONCE(cnt < 0);
>  	}
>  
> -	if (!n_normal_preds || n_logical_preds >= n_normal_preds) {
> +	if (cnt != 1 || !n_normal_preds || n_logical_preds >= n_normal_preds) {
>  		parse_error(ps, FILT_ERR_INVALID_FILTER, 0);
>  		return -EINVAL;
>  	}