selftests/bpf: Fix file descriptor leak in load_kallsyms()

Currently, if sym_cnt > 0, it just returns and does not close file, fix it.
Signed-off-by: Yuntao Wang <ytcoode@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20220405145711.49543-1-ytcoode@gmail.com

tools/testing/selftests/bpf/trace_helpers.c

@@ -25,15 +25,12 @@ static int ksym_cmp(const void *p1, const void *p2)
 
 int load_kallsyms(void)
 {
-	FILE *f = fopen("/proc/kallsyms", "r");
+	FILE *f;
 	char func[256], buf[256];
 	char symbol;
 	void *addr;
 	int i = 0;
 
-	if (!f)
-		return -ENOENT;
-
 	/*
 	 * This is called/used from multiplace places,
 	 * load symbols just once.
@@ -41,6 +38,10 @@ int load_kallsyms(void)
 	if (sym_cnt)
 		return 0;
 
+	f = fopen("/proc/kallsyms", "r");
+	if (!f)
+		return -ENOENT;
+
 	while (fgets(buf, sizeof(buf), f)) {
 		if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
 			break;