patch "USB: serial: ftdi_sio: fix line-status over-reporting" added to usb-next

patch "USB: serial: ftdi_sio: fix line-status over-reporting" added to usb-next

[gregkh]

This is a note to let you know that I've just added the patch titled

    USB: serial: ftdi_sio: fix line-status over-reporting

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From a6bb1e17a39818b01b55d8e6238b4b5f06d55038 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Thu, 2 Feb 2017 17:38:35 +0100
Subject: USB: serial: ftdi_sio: fix line-status over-reporting

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 <michael@walle.cc>
Fixes: 72fda3ca6fc1 ("USB: serial: ftd_sio: implement sysrq handling on
break")
Fixes: 166ceb690750 ("USB: ftdi_sio: clean up line-status handling")
Cc: stable <stable@vger.kernel.org>	# v2.6.35
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/ftdi_sio.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index e82dbb3d0883..c540de15aad2 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2068,6 +2068,20 @@ static int ftdi_process_packet(struct usb_serial_port *port,
 		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
@@ -2090,15 +2104,6 @@ static int ftdi_process_packet(struct usb_serial_port *port,
 		}
 	}
 
-	/* 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;
 
-- 
2.11.1