Patch "USB: serial: ch341: fix modem-status handling" has been added to the 4.10-stable tree

[<gregkh@linuxfoundation.org>]

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

    USB: serial: ch341: fix modem-status handling

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-ch341-fix-modem-status-handling.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 <stable@vger.kernel.org> know about it.


>From a0467a967f347842b30739aae636c44980265265 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Fri, 6 Jan 2017 19:15:17 +0100
Subject: USB: serial: ch341: fix modem-status handling

From: Johan Hovold <johan@kernel.org>

commit a0467a967f347842b30739aae636c44980265265 upstream.

The modem-status register was read as part of device configuration at
port_probe and then again at open (and reset-resume). During open (and
reset-resume) the MSR was read before submitting the interrupt URB,
something which could lead to an MSR-change going unnoticed when it
races with open (reset-resume).

Fix this by dropping the redundant reconfiguration of the port at every
open, and only read the MSR after the interrupt URB has been submitted.

Fixes: 664d5df92e88 ("USB: usb-serial ch341: support for DTR/RTS/CTS")
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 drivers/usb/serial/ch341.c |   27 ++++++++++++---------------
 1 file changed, 12 insertions(+), 15 deletions(-)

--- a/drivers/usb/serial/ch341.c
+++ b/drivers/usb/serial/ch341.c
@@ -248,21 +248,11 @@ static int ch341_configure(struct usb_de
 	if (r < 0)
 		goto out;
 
-	/* expect 0xff 0xee */
-	r = ch341_get_status(dev, priv);
-	if (r < 0)
-		goto out;
-
 	r = ch341_set_baudrate_lcr(dev, priv, priv->lcr);
 	if (r < 0)
 		goto out;
 
 	r = ch341_set_handshake(dev, priv->line_control);
-	if (r < 0)
-		goto out;
-
-	/* expect 0x9f 0xee */
-	r = ch341_get_status(dev, priv);
 
 out:	kfree(buffer);
 	return r;
@@ -334,14 +324,9 @@ static void ch341_close(struct usb_seria
 /* open this device, set default parameters */
 static int ch341_open(struct tty_struct *tty, struct usb_serial_port *port)
 {
-	struct usb_serial *serial = port->serial;
 	struct ch341_private *priv = usb_get_serial_port_data(port);
 	int r;
 
-	r = ch341_configure(serial->dev, priv);
-	if (r)
-		return r;
-
 	if (tty)
 		ch341_set_termios(tty, port, NULL);
 
@@ -353,6 +338,12 @@ static int ch341_open(struct tty_struct
 		return r;
 	}
 
+	r = ch341_get_status(port->serial->dev, priv);
+	if (r < 0) {
+		dev_err(&port->dev, "failed to read modem status: %d\n", r);
+		goto err_kill_interrupt_urb;
+	}
+
 	r = usb_serial_generic_open(tty, port);
 	if (r)
 		goto err_kill_interrupt_urb;
@@ -619,6 +610,12 @@ static int ch341_reset_resume(struct usb
 				ret);
 			return ret;
 		}
+
+		ret = ch341_get_status(port->serial->dev, priv);
+		if (ret < 0) {
+			dev_err(&port->dev, "failed to read modem status: %d\n",
+				ret);
+		}
 	}
 
 	return usb_serial_generic_resume(serial);


Patches currently in stable-queue which might be from johan@kernel.org are

queue-4.10/usb-serial-mct_u232-fix-modem-status-error-handling.patch
queue-4.10/usb-serial-ark3116-fix-open-error-handling.patch
queue-4.10/usb-serial-io_edgeport-fix-epic-descriptor-handling.patch
queue-4.10/usb-serial-ti_usb_3410_5052-fix-control-message-error-handling.patch
queue-4.10/usb-serial-keyspan_pda-fix-receive-sanity-checks.patch
queue-4.10/usb-serial-sierra-fix-bogus-alternate-setting-assumption.patch
queue-4.10/usb-serial-ssu100-fix-control-message-error-handling.patch
queue-4.10/usb-serial-digi_acceleport-fix-incomplete-rx-sanity-check.patch
queue-4.10/usb-serial-ch341-fix-modem-status-handling.patch
queue-4.10/usb-serial-io_edgeport-fix-descriptor-error-handling.patch
queue-4.10/usb-serial-quatech2-fix-control-message-error-handling.patch
queue-4.10/usb-serial-ftdi_sio-fix-latency-timer-error-handling.patch