From: Johan Hovold <johan@kernel.org>
Date: Thu, 12 Jan 2017 13:56:16 +0000 (+0100)
Subject: USB: serial: mct_u232: fix modem-status error handling
X-Git-Tag: v3.2.89~88
X-Git-Url: https://git.openpandora.org/cgi-bin/gitweb.cgi?p=pandora-kernel.git;a=commitdiff_plain;h=56a8299247d068b1318813ff772f791e4f8bbfa0

USB: serial: mct_u232: fix modem-status error handling

commit 36356a669eddb32917fc4b5c2b9b8bf80ede69de upstream.

Make sure to detect short control-message transfers so that errors are
logged when reading the modem status at open.

Note that while this also avoids initialising the modem status using
uninitialised heap data, these bits could not leak to user space as they
are currently not used.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

diff --git a/drivers/usb/serial/mct_u232.c b/drivers/usb/serial/mct_u232.c
index a7e7ba65a611..801c697148ef 100644
--- a/drivers/usb/serial/mct_u232.c
+++ b/drivers/usb/serial/mct_u232.c
@@ -385,9 +385,13 @@ static int mct_u232_get_modem_stat(struct usb_serial *serial,
 			MCT_U232_GET_REQUEST_TYPE,
 			0, 0, buf, MCT_U232_GET_MODEM_STAT_SIZE,
 			WDR_TIMEOUT);
-	if (rc < 0) {
+	if (rc < MCT_U232_GET_MODEM_STAT_SIZE) {
 		dev_err(&serial->dev->dev,
 			"Get MODEM STATus failed (error = %d)\n", rc);
+
+		if (rc >= 0)
+			rc = -EIO;
+
 		*msr = 0;
 	} else {
 		*msr = buf[0];