selinux: fix memleak in security_read_state_kernel()

In this function, it directly returns the result of __security_read_policy
without freeing the allocated memory in *data, cause memory leak issue,
so free the memory if __security_read_policy failed.

Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
[PM: subject line tweak]
Signed-off-by: Paul Moore <paul@paul-moore.com>

security/selinux/ss/services.c

@@ -4048,6 +4048,7 @@ int security_read_policy(struct selinux_state *state,
 int security_read_state_kernel(struct selinux_state *state,
 			       void **data, size_t *len)
 {
+	int err;
 	struct selinux_policy *policy;
 
 	policy = rcu_dereference_protected(
@@ -4060,5 +4061,11 @@ int security_read_state_kernel(struct selinux_state *state,
 	if (!*data)
 		return -ENOMEM;
 
-	return __security_read_policy(policy, *data, len);
+	err = __security_read_policy(policy, *data, len);
+	if (err) {
+		vfree(*data);
+		*data = NULL;
+		*len = 0;
+	}
+	return err;
 }