b2c2-flexcop-usb: add sanity checking

hulk inclusion
category: bugfix
bugzilla: 13690
CVE: CVE-2019-15291

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

The driver needs an isochronous endpoint to be present. It will
oops in its absence. Add checking for it.

Reported-by: syzbot+d93dff37e6a89431c158@syzkaller.appspotmail.com
Signed-off-by: NOliver Neukum <oneukum@suse.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>
Reviewed-by: NZhen Lei <thunder.leizhen@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

drivers/media/usb/b2c2/flexcop-usb.c

@@ -537,6 +537,9 @@ static int flexcop_usb_probe(struct usb_interface *intf,
 	struct flexcop_device *fc = NULL;
 	int ret;
 
+	if (intf->cur_altsetting->desc.bNumEndpoints < 1)
+		return -ENODEV;
+
 	if ((fc = flexcop_device_kmalloc(sizeof(struct flexcop_usb))) == NULL) {
 		err("out of memory\n");
 		return -ENOMEM;