Patch "USB: serial: ftdi_sio: fix line-status over-reporting" has been added to the 4.10-stable tree

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 the 4.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
usb-serial-ftdi_sio-fix-line-status-over-reporting.patch
and it can be found in the queue-4.10 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Johan Hovold <[email protected]>
Date: Thu, 2 Feb 2017 17:38:35 +0100
Subject: USB: serial: ftdi_sio: fix line-status over-reporting

From: Johan Hovold <[email protected]>

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.

break")

---
 drivers/usb/serial/ftdi_sio.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

@@ -2065,6 +2065,20 @@ 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

@@ -2087,15 +2101,6 @@ 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;
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.10/usb-serial-ftdi_sio-fix-modem-status-error-handling.patch queue-4.10/usb-serial-cp210x-add-new-ids-for-ge-bx50v3-boards.patch queue-4.10/usb-serial-ark3116-fix-register-accessor-error-handling.patch queue-4.10/usb-serial-digi_acceleport-fix-oob-data-sanity-check.patch queue-4.10/usb-serial-ftdi_sio-fix-line-status-over-reporting.patch queue-4.10/usb-serial-ftdi_sio-fix-extreme-low-latency-setting.patch queue-4.10/usb-serial-spcp8x5-fix-modem-status-handling.patch queue-4.10/usb-serial-opticon-fix-cts-retrieval-at-open.patch queue-4.10/usb-serial-mos7840-fix-another-null-deref-at-open.patch queue-4.10/usb-serial-console-fix-uninitialised-spinlock.patch