perf tools: Use zfree to help detect use after free bugs

Several areas already used this technique, so do some audit to
consistently use it elsewhere.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-9sbere0kkplwe45ak6rk4a1f@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/comm.c b/tools/perf/util/comm.c
index ee0df0e..67d1e40 100644
--- a/tools/perf/util/comm.c
+++ b/tools/perf/util/comm.c
@@ -21,7 +21,7 @@
 {
 	if (!--cs->ref) {
 		rb_erase(&cs->rb_node, &comm_str_root);
-		free(cs->str);
+		zfree(&cs->str);
 		free(cs);
 	}
 }