Fix BIO_push ref counting for SSL BIO

When pushing a BIO onto an SSL BIO we set the rbio and wbio for the SSL
object to be the BIO that has been pushed. Therefore we need to up the ref
count for that BIO. The existing code was uping the ref count on the wrong
BIO.
Reviewed-by: NRich Salz <rsalz@openssl.org>

ssl/bio_ssl.c

@@ -327,8 +327,12 @@ static long ssl_ctrl(BIO *b, int cmd, long num, void *ptr)
         break;
     case BIO_CTRL_PUSH:
         if ((next != NULL) && (next != ssl->rbio)) {
+            /*
+             * We are going to pass ownership of next to the SSL object...but
+             * we don't own a reference to pass yet - so up ref
+             */
+            BIO_up_ref(next);
             SSL_set_bio(ssl, next, next);
-            BIO_up_ref(b);
         }
         break;
     case BIO_CTRL_POP: