perf metricgroup: Fix use after free in metric__new()

We shouldn't free() something that will be used in the next line, fix
it.

Fixes: b85a4d6 ("perf metric: Allow modifiers on metrics")
Addresses-Coverity-ID: 1494000
Signed-off-by: José Expósito <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andi Kleen <[email protected]>
Cc: Ian Rogers <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: John Garry <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: JoseExposito

tools/perf/util/metricgroup.c

@@ -209,8 +209,8 @@ static struct metric *metric__new(const struct pmu_event *pe,
 	m->metric_name = pe->metric_name;
 	m->modifier = modifier ? strdup(modifier) : NULL;
 	if (modifier && !m->modifier) {
-		free(m);
 		expr__ctx_free(m->pctx);
+		free(m);
 		return NULL;
 	}
 	m->metric_expr = pe->metric_expr;