perf list: Use zfree() to reduce chances of use after free

Do defensive programming by using zfree() to initialize freed pointers
to NULL, so that eventual use after free result in a NULL pointer deref
instead of more subtle behaviour.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

diff --git a/tools/perf/builtin-list.c b/tools/perf/builtin-list.c
index 29f09ce..1f5dbd5 100644 (file)
--- a/tools/perf/builtin-list.c
+++ b/tools/perf/builtin-list.c
@@ -127,7 +127,7 @@ static void default_print_event(void *ps, const char *pmu_name, const char *topi
        if (strcmp(print_state->last_topic, topic ?: "")) {
                if (topic)
                        printf("\n%s:\n", topic);
-               free(print_state->last_topic);
+               zfree(&print_state->last_topic);
                print_state->last_topic = strdup(topic ?: "");
        }
 
@@ -197,7 +197,7 @@ static void default_print_metric(void *ps,
                        else
                                printf("%s\n", group);
                }
-               free(print_state->last_metricgroups);
+               zfree(&print_state->last_metricgroups);
                print_state->last_metricgroups = strdup(group ?: "");
        }
        if (!print_state->metrics)