From patchwork Wed Mar 16 14:36:44 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wander Lairson Costa X-Patchwork-Id: 552500 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 829FAC433EF for ; Wed, 16 Mar 2022 14:38:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1348341AbiCPOjN (ORCPT ); Wed, 16 Mar 2022 10:39:13 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37362 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1356549AbiCPOjK (ORCPT ); Wed, 16 Mar 2022 10:39:10 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id B27C8326 for ; Wed, 16 Mar 2022 07:37:56 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1647441475; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=FdaRFj6Txp5dVh+5ToS7luAujkKT+3c923Qns25TpZk=; b=eF9HrZBMUMOCjz+Bgb7263C8DaJlcYicUn09+viv6d/yvstNHxlkTzgR3lkvMdWhw6fEqL /9rzwhql0c7XJDhRhM4Oc/F/9MaEdKyRg1DS/FHeGdSZSaPJvo4FgyYaMareXdb4wZD4fV J0piltlXplrvu6HgSe/z9qtAdQEDJf0= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-520-PX3TcyXXMn21kXKpX9Klgg-1; Wed, 16 Mar 2022 10:37:52 -0400 X-MC-Unique: PX3TcyXXMn21kXKpX9Klgg-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.rdu2.redhat.com [10.11.54.1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 453D91801388; Wed, 16 Mar 2022 14:37:51 +0000 (UTC) Received: from fedora.redhat.com (unknown [10.22.19.38]) by smtp.corp.redhat.com (Postfix) with ESMTP id 132C1400F73E; Wed, 16 Mar 2022 14:37:47 +0000 (UTC) From: Wander Lairson Costa To: Greg Kroah-Hartman , Jiri Slaby , Johan Hovold , Wander Lairson Costa , "Maciej W. Rozycki" , Serge Semin , Lukas Wunner , =?utf-8?q?Pali_Roh=C3=A1r?= , linux-serial@vger.kernel.org (open list:SERIAL DRIVERS), linux-kernel@vger.kernel.org (open list) Cc: rostedt@goodmis.org, senozhatsky@chromium.org, andre.goddard@gmail.com, sudipm.mukherjee@gmail.com, andy.shevchenko@gmail.com, David.Laight@aculab.com, jonathanh@nvidia.com, phil@raspberrypi.com Subject: [PATCH v4 5/5] serial/8250: Only use fifo after the port is initialized in console_write Date: Wed, 16 Mar 2022 11:36:44 -0300 Message-Id: <20220316143646.13301-6-wander@redhat.com> In-Reply-To: <20220316143646.13301-1-wander@redhat.com> References: <20220316143646.13301-1-wander@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.84 on 10.11.54.1 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org The serial driver set the value of uart_8250_port.fcr in the function serial8250_config_port, but only writes the value to the controller register later in the initalization code. That opens a small window in which is not safe to use the fifo for console write. Make sure the port is initialized correctly before reading the FCR cached value. Unfortunately, I lost track of who originally reported the issue. If s/he is reading this, please speak up so I can give you the due credit. Signed-off-by: Wander Lairson Costa --- drivers/tty/serial/8250/8250_port.c | 1 + 1 file changed, 1 insertion(+) diff --git a/drivers/tty/serial/8250/8250_port.c b/drivers/tty/serial/8250/8250_port.c index 4acf620be241..7e2227161555 100644 --- a/drivers/tty/serial/8250/8250_port.c +++ b/drivers/tty/serial/8250/8250_port.c @@ -3416,6 +3416,7 @@ void serial8250_console_write(struct uart_8250_port *up, const char *s, !(up->capabilities & UART_CAP_MINI) && up->tx_loadsz > 1 && (up->fcr & UART_FCR_ENABLE_FIFO) && + test_bit(TTY_PORT_INITIALIZED, &port->state->port.iflags) && /* * After we put a data in the fifo, the controller will send * it regardless of the CTS state. Therefore, only use fifo