linux-kernel - [PATCH 3.16 040/212] USB: serial: ch341: fix modem-status handling

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <lsq.1496331795.95116277@decadent.org.uk>
Date:   Thu, 01 Jun 2017 16:43:15 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Johan Hovold" <johan@...nel.org>
Subject: [PATCH 3.16 040/212] USB: serial: ch341: fix modem-status handling

3.16.44-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Johan Hovold <johan@...nel.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@...nel.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 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
@@ -246,21 +246,11 @@ 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, 0);
 	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;
@@ -332,14 +322,9 @@ 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);
 
@@ -351,6 +336,12 @@ 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;
@@ -593,6 +584,12 @@ 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);