linux-kernel - [PATCH 3.16 165/370] USB: serial: mos7720: fix parport use-after-free on probe errors

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Message-ID: <lsq.1489146382.407666628@decadent.org.uk>
Date:   Fri, 10 Mar 2017 11:46:22 +0000
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 3.16 165/370] USB: serial: mos7720: fix parport
 use-after-free on probe errors

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

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

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

commit 75dd211e773afcbc264677b0749d1cf7d937ab2d upstream.

Do not submit the interrupt URB until after the parport has been
successfully registered to avoid another use-after-free in the
completion handler when accessing the freed parport private data in case
of a racing completion.

Fixes: b69578df7e98 ("USB: usbserial: mos7720: add support for parallel
port on moschip 7715")
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/usb/serial/mos7720.c | 18 ++++++++----------
 1 file changed, 8 insertions(+), 10 deletions(-)

--- a/drivers/usb/serial/mos7720.c
+++ b/drivers/usb/serial/mos7720.c
@@ -1936,22 +1936,20 @@ static int mos7720_startup(struct usb_se
 	usb_control_msg(serial->dev, usb_sndctrlpipe(serial->dev, 0),
 			(__u8)0x03, 0x00, 0x01, 0x00, NULL, 0x00, 5000);
 
-	/* start the interrupt urb */
-	ret_val = usb_submit_urb(serial->port[0]->interrupt_in_urb, GFP_KERNEL);
-	if (ret_val)
-		dev_err(&dev->dev,
-			"%s - Error %d submitting control urb\n",
-			__func__, ret_val);
-
 #ifdef CONFIG_USB_SERIAL_MOS7715_PARPORT
 	if (product == MOSCHIP_DEVICE_ID_7715) {
 		ret_val = mos7715_parport_init(serial);
-		if (ret_val < 0) {
-			usb_kill_urb(serial->port[0]->interrupt_in_urb);
+		if (ret_val < 0)
 			return ret_val;
-		}
 	}
 #endif
+	/* start the interrupt urb */
+	ret_val = usb_submit_urb(serial->port[0]->interrupt_in_urb, GFP_KERNEL);
+	if (ret_val) {
+		dev_err(&dev->dev, "failed to submit interrupt urb: %d\n",
+			ret_val);
+	}
+
 	/* LSR For Port 1 */
 	read_mos_reg(serial, 0, LSR, &data);
 	dev_dbg(&dev->dev, "LSR:%x\n", data);