linux-kernel - [PATCH 3.10 126/250] USB: serial: mos7840: fix another NULL-deref at open

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Message-Id: <1496876436-32402-127-git-send-email-w@1wt.eu>
Date:   Thu,  8 Jun 2017 00:58:32 +0200
From:   Willy Tarreau <w@....eu>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        linux@...ck-us.net
Cc:     Johan Hovold <johan@...nel.org>, Willy Tarreau <w@....eu>
Subject: [PATCH 3.10 126/250] USB: serial: mos7840: fix another NULL-deref at open

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

commit 5182c2cf2a9bfb7f066ef0bdd2bb6330b94dd74e upstream.

Fix another NULL-pointer dereference at open should a malicious device
lack an interrupt-in endpoint.

Note that the driver has a broken check for an interrupt-in endpoint
which means that an interrupt URB has never even been submitted.

Fixes: 3f5429746d91 ("USB: Moschip 7840 USB-Serial Driver")
Reviewed-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Johan Hovold <johan@...nel.org>
Signed-off-by: Willy Tarreau <w@....eu>
---
 drivers/usb/serial/mos7840.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/serial/mos7840.c b/drivers/usb/serial/mos7840.c
index 5041b6c..3308c43 100644
--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -1041,6 +1041,7 @@ static int mos7840_open(struct tty_struct *tty, struct usb_serial_port *port)
 	 * (can't set it up in mos7840_startup as the structures *
 	 * were not set up at that time.)                        */
 	if (port0->open_ports == 1) {
+		/* FIXME: Buffer never NULL, so URB is not submitted. */
 		if (serial->port[0]->interrupt_in_buffer == NULL) {
 			/* set up interrupt urb */
 			usb_fill_int_urb(serial->port[0]->interrupt_in_urb,
@@ -2258,7 +2259,8 @@ static int mos7840_calc_num_ports(struct usb_serial *serial)
 static int mos7840_attach(struct usb_serial *serial)
 {
 	if (serial->num_bulk_in < serial->num_ports ||
-			serial->num_bulk_out < serial->num_ports) {
+			serial->num_bulk_out < serial->num_ports ||
+			serial->num_interrupt_in < 1) {
 		dev_err(&serial->interface->dev, "missing endpoints\n");
 		return -ENODEV;
 	}
-- 
2.8.0.rc2.1.gbe9624a