separate BAD_FUNC_ARG error from ASN_NO_PEM_HEADER

Author: rlm2002

src/x509.c

@@ -12368,7 +12368,14 @@ WOLFSSL_X509_CRL* wolfSSL_PEM_read_X509_CRL(XFILE fp,
             return WOLFSSL_FAILURE;
         }
 
-        if ((l = wolfSSL_BIO_get_len(bio)) <= pem_struct_min_sz) {
+        l = wolfSSL_BIO_get_len(bio);
+
+        if (l < 0) {
+            WOLFSSL_ERROR(BAD_FUNC_ARG);
+            return WOLFSSL_FAILURE;
+        }
+
+        if (l <= pem_struct_min_sz) {
             /* No certificate in buffer */
             WOLFSSL_ERROR(ASN_NO_PEM_HEADER);
             return WOLFSSL_FAILURE;