staging: wlan-ng: fix out of bounds read in prism2sta_probe_usb()

let's use usb_find_common_endpoints() to discover endpoints, it does all
necessary checks for type and xfer direction

remove memset() in hfa384x_create(), because we now assign endpoints in
prism2sta_probe_usb() and because create_wlan() uses kzalloc() to
allocate hfa384x struct before calling hfa384x_create()

Fixes: faaff976 ("staging: wlan-ng: properly check endpoint types")
Reported-and-tested-by: syzbot+22794221ab96b0bab53a@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=22794221ab96b0bab53aSigned-off-by: Rustam Kovhaev <rkovhaev@gmail.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20200804145614.104320-1-rkovhaev@gmail.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wlan-ng/hfa384x_usb.c

@@ -524,13 +524,8 @@ static void hfa384x_usb_defer(struct work_struct *data)
  */
 void hfa384x_create(struct hfa384x *hw, struct usb_device *usb)
 {
-	memset(hw, 0, sizeof(*hw));
 	hw->usb = usb;
 
-	/* set up the endpoints */
-	hw->endp_in = usb_rcvbulkpipe(usb, 1);
-	hw->endp_out = usb_sndbulkpipe(usb, 2);
-
 	/* Set up the waitq */
 	init_waitqueue_head(&hw->cmdq);
 

drivers/staging/wlan-ng/prism2usb.c

@@ -61,23 +61,14 @@ static int prism2sta_probe_usb(struct usb_interface *interface,
 			       const struct usb_device_id *id)
 {
 	struct usb_device *dev;
-	const struct usb_endpoint_descriptor *epd;
-	const struct usb_host_interface *iface_desc = interface->cur_altsetting;
+	struct usb_endpoint_descriptor *bulk_in, *bulk_out;
+	struct usb_host_interface *iface_desc = interface->cur_altsetting;
 	struct wlandevice *wlandev = NULL;
 	struct hfa384x *hw = NULL;
 	int result = 0;
 
-	if (iface_desc->desc.bNumEndpoints != 2) {
-		result = -ENODEV;
-		goto failed;
-	}
-
-	result = -EINVAL;
-	epd = &iface_desc->endpoint[1].desc;
-	if (!usb_endpoint_is_bulk_in(epd))
-		goto failed;
-	epd = &iface_desc->endpoint[2].desc;
-	if (!usb_endpoint_is_bulk_out(epd))
+	result = usb_find_common_endpoints(iface_desc, &bulk_in, &bulk_out, NULL, NULL);
+	if (result)
 		goto failed;
 
 	dev = interface_to_usbdev(interface);
@@ -96,6 +87,8 @@ static int prism2sta_probe_usb(struct usb_interface *interface,
 	}
 
 	/* Initialize the hw data */
+	hw->endp_in = usb_rcvbulkpipe(dev, bulk_in->bEndpointAddress);
+	hw->endp_out = usb_sndbulkpipe(dev, bulk_out->bEndpointAddress);
 	hfa384x_create(hw, dev);
 	hw->wlandev = wlandev;