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

BugLink: https://bugs.launchpad.net/bugs/2041702

[ Upstream commit 9997d5d ]

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>
Stable-dep-of: 7962ef1 ("perf trace: Really free the evsel->priv area")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

Author: acmel

tools/perf/builtin-trace.c

@@ -2287,7 +2287,7 @@ static void syscall__exit(struct syscall *sc)
 	if (!sc)
 		return;
 
-	free(sc->arg_fmt);
+	zfree(&sc->arg_fmt);
 }
 
 static int trace__sys_enter(struct trace *trace, struct evsel *evsel,
@@ -3129,7 +3129,7 @@ static void evlist__free_syscall_tp_fields(struct evlist *evlist)
 		if (!et || !evsel->tp_format || strcmp(evsel->tp_format->system, "syscalls"))
 			continue;
 
-		free(et->fmt);
+		zfree(&et->fmt);
 		free(et);
 	}
 }
@@ -4748,11 +4748,11 @@ static void trace__exit(struct trace *trace)
 	int i;
 
 	strlist__delete(trace->ev_qualifier);
-	free(trace->ev_qualifier_ids.entries);
+	zfree(&trace->ev_qualifier_ids.entries);
 	if (trace->syscalls.table) {
 		for (i = 0; i <= trace->sctbl->syscalls.max_id; i++)
 			syscall__exit(&trace->syscalls.table[i]);
-		free(trace->syscalls.table);
+		zfree(&trace->syscalls.table);
 	}
 	syscalltbl__delete(trace->sctbl);
 	zfree(&trace->perfconfig_events);