[PATCH 4.4 12/25] USB: serial: mos7840: fix another NULL-deref at open

Greg Kroah-Hartman
2017-02-24T08:37:22Z

From: Johan Hovold <johan@kernel.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@linuxfoundation.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/usb/serial/mos7840.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/usb/serial/mos7840.c
+++ b/drivers/usb/serial/mos7840.c
@@ -1024,6 +1024,7 @@ static int mos7840_open(struct tty_struc
* (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,
@@ -2119,7 +2120,8 @@ static int mos7840_calc_num_ports(struct
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;
}