linux-kernel - [PATCH review for 4.4 23/47] USB: serial: mos7840: fix control-message error handling

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Message-ID: <20170920044445.7392-23-alexander.levin@verizon.com>
Date:   Wed, 20 Sep 2017 04:45:05 +0000
From:   "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>
Cc:     Johan Hovold <johan@...nel.org>,
        "Levin, Alexander (Sasha Levin)" <alexander.levin@...izon.com>
Subject: [PATCH review for 4.4 23/47] USB: serial: mos7840: fix
 control-message error handling

From: Johan Hovold <johan@...nel.org>

[ Upstream commit cd8db057e93ddaacbec025b567490555d2bca280 ]

Make sure to detect short transfers when reading a device register.

The modem-status handling had sufficient error checks in place, but move
handling of short transfers into the register accessor function itself
for consistency.

Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
---
 drivers/usb/serial/mos7840.c | 19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index d17685cc00c9..ed883a7ad533 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -285,9 +285,15 @@ static int mos7840_get_reg_sync(struct usb_serial_port *port, __u16 reg,
 	ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), MCS_RDREQ,
 			      MCS_RD_RTYPE, 0, reg, buf, VENDOR_READ_LENGTH,
 			      MOS_WDR_TIMEOUT);
+	if (ret < VENDOR_READ_LENGTH) {
+		if (ret >= 0)
+			ret = -EIO;
+		goto out;
+	}
+
 	*val = buf[0];
 	dev_dbg(&port->dev, "%s offset is %x, return val %x\n", __func__, reg, *val);
-
+out:
 	kfree(buf);
 	return ret;
 }
@@ -353,8 +359,13 @@ static int mos7840_get_uart_reg(struct usb_serial_port *port, __u16 reg,
 	ret = usb_control_msg(dev, usb_rcvctrlpipe(dev, 0), MCS_RDREQ,
 			      MCS_RD_RTYPE, Wval, reg, buf, VENDOR_READ_LENGTH,
 			      MOS_WDR_TIMEOUT);
+	if (ret < VENDOR_READ_LENGTH) {
+		if (ret >= 0)
+			ret = -EIO;
+		goto out;
+	}
 	*val = buf[0];
-
+out:
 	kfree(buf);
 	return ret;
 }
@@ -1490,10 +1501,10 @@ static int mos7840_tiocmget(struct tty_struct *tty)
 		return -ENODEV;
 
 	status = mos7840_get_uart_reg(port, MODEM_STATUS_REGISTER, &msr);
-	if (status != 1)
+	if (status < 0)
 		return -EIO;
 	status = mos7840_get_uart_reg(port, MODEM_CONTROL_REGISTER, &mcr);
-	if (status != 1)
+	if (status < 0)
 		return -EIO;
 	result = ((mcr & MCR_DTR) ? TIOCM_DTR : 0)
 	    | ((mcr & MCR_RTS) ? TIOCM_RTS : 0)
-- 
2.11.0