Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752236AbdFAQS1 (ORCPT ); Thu, 1 Jun 2017 12:18:27 -0400 Received: from shadbolt.e.decadent.org.uk ([88.96.1.126]:33475 "EHLO shadbolt.e.decadent.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752116AbdFAPo5 (ORCPT ); Thu, 1 Jun 2017 11:44:57 -0400 Content-Type: text/plain; charset="UTF-8" Content-Disposition: inline Content-Transfer-Encoding: 8bit MIME-Version: 1.0 From: Ben Hutchings To: linux-kernel@vger.kernel.org, stable@vger.kernel.org CC: akpm@linux-foundation.org, "Johan Hovold" , "Michael Walle" Date: Thu, 01 Jun 2017 16:43:16 +0100 Message-ID: X-Mailer: LinuxStableQueue (scripts by bwh) Subject: [PATCH 3.16 103/212] USB: serial: ftdi_sio: fix line-status over-reporting In-Reply-To: X-SA-Exim-Connect-IP: 82.70.136.246 X-SA-Exim-Mail-From: ben@decadent.org.uk X-SA-Exim-Scanned: No (on shadbolt.decadent.org.uk); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2213 Lines: 73 3.16.44-rc1 review patch. If anyone has any objections, please let me know. ------------------ From: Johan Hovold commit a6bb1e17a39818b01b55d8e6238b4b5f06d55038 upstream. FTDI devices use a receive latency timer to periodically empty the receive buffer and report modem and line status (also when the buffer is empty). When a break or error condition is detected the corresponding status flags will be set on a packet with nonzero data payload and the flags are not updated until the break is over or further characters are received. In order to avoid over-reporting break and error conditions, these flags must therefore only be processed for packets with payload. This specifically fixes the case where after an overrun, the error condition is continuously reported and NULL-characters inserted until further data is received. Reported-by: Michael Walle Fixes: 72fda3ca6fc1 ("USB: serial: ftd_sio: implement sysrq handling on break") Fixes: 166ceb690750 ("USB: ftdi_sio: clean up line-status handling") Signed-off-by: Johan Hovold Signed-off-by: Ben Hutchings --- drivers/usb/serial/ftdi_sio.c | 23 ++++++++++++++--------- 1 file changed, 14 insertions(+), 9 deletions(-) --- a/drivers/usb/serial/ftdi_sio.c +++ b/drivers/usb/serial/ftdi_sio.c @@ -2109,6 +2109,20 @@ static int ftdi_process_packet(struct us priv->prev_status = status; } + /* save if the transmitter is empty or not */ + if (packet[1] & FTDI_RS_TEMT) + priv->transmit_empty = 1; + else + priv->transmit_empty = 0; + + len -= 2; + if (!len) + return 0; /* status only */ + + /* + * Break and error status must only be processed for packets with + * data payload to avoid over-reporting. + */ flag = TTY_NORMAL; if (packet[1] & FTDI_RS_ERR_MASK) { /* Break takes precedence over parity, which takes precedence @@ -2131,15 +2145,6 @@ static int ftdi_process_packet(struct us } } - /* save if the transmitter is empty or not */ - if (packet[1] & FTDI_RS_TEMT) - priv->transmit_empty = 1; - else - priv->transmit_empty = 0; - - len -= 2; - if (!len) - return 0; /* status only */ port->icount.rx += len; ch = packet + 2;