patch "USB: serial: ftdi_sio: fix modem-status error handling" added to usb-next

patch "USB: serial: ftdi_sio: fix modem-status error handling" added to usb-next

[gregkh]

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

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

to my usb git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git
in the usb-next branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will also be merged in the next major kernel release
during the merge window.

If you have any questions about this process, please let me know.


>From 427c3a95e3e29e65f59d99aaf320d7506f3eed57 Mon Sep 17 00:00:00 2001
From: Johan Hovold <johan@kernel.org>
Date: Thu, 12 Jan 2017 14:56:11 +0100
Subject: USB: serial: ftdi_sio: fix modem-status error handling

Make sure to detect short responses when fetching the modem status in
order to avoid parsing uninitialised buffer data and having bits of it
leak to user space.

Note that we still allow for short 1-byte responses.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
---
 drivers/usb/serial/ftdi_sio.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/ftdi_sio.c b/drivers/usb/serial/ftdi_sio.c
index 23d14b98ae2a..6dee20fc7e45 100644
--- a/drivers/usb/serial/ftdi_sio.c
+++ b/drivers/usb/serial/ftdi_sio.c
@@ -2428,8 +2428,12 @@ static int ftdi_get_modem_status(struct usb_serial_port *port,
 			FTDI_SIO_GET_MODEM_STATUS_REQUEST_TYPE,
 			0, priv->interface,
 			buf, len, WDR_TIMEOUT);
-	if (ret < 0) {
+
+	/* NOTE: We allow short responses and handle that below. */
+	if (ret < 1) {
 		dev_err(&port->dev, "failed to get modem status: %d\n", ret);
+		if (ret >= 0)
+			ret = -EIO;
 		ret = usb_translate_errors(ret);
 		goto out;
 	}
-- 
2.11.1