media: dvb-usb-v2: lmedm04: Improve logic checking of warm start

commit 3d932ee2 upstream.

Warm start has no check as whether a genuine device has
connected and proceeds to next execution path.

Check device should read 0x47 at offset of 2 on USB descriptor read
and it is the amount requested of 6 bytes.

Fix for
kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access as
Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Malcolm Priestley <tvboxspy@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Cc: Ben Hutchings <ben.hutchings@codethink.co.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/media/usb/dvb-usb-v2/lmedm04.c

@@ -503,18 +503,23 @@ static int lme2510_pid_filter(struct dvb_usb_adapter *adap, int index, u16 pid,
 
 static int lme2510_return_status(struct dvb_usb_device *d)
 {
-	int ret = 0;
+	int ret;
 	u8 *data;
 
-	data = kzalloc(10, GFP_KERNEL);
+	data = kzalloc(6, GFP_KERNEL);
 	if (!data)
 		return -ENOMEM;
 
-	ret |= usb_control_msg(d->udev, usb_rcvctrlpipe(d->udev, 0),
-			0x06, 0x80, 0x0302, 0x00, data, 0x0006, 200);
-	info("Firmware Status: %x (%x)", ret , data[2]);
+	ret = usb_control_msg(d->udev, usb_rcvctrlpipe(d->udev, 0),
+			      0x06, 0x80, 0x0302, 0x00,
+			      data, 0x6, 200);
+	if (ret != 6)
+		ret = -EINVAL;
+	else
+		ret = data[2];
+
+	info("Firmware Status: %6ph", data);
 
-	ret = (ret < 0) ? -ENODEV : data[2];
 	kfree(data);
 	return ret;
 }
@@ -1199,6 +1204,7 @@ static int lme2510_get_adapter_count(struct dvb_usb_device *d)
 static int lme2510_identify_state(struct dvb_usb_device *d, const char **name)
 {
 	struct lme2510_state *st = d->priv;
+	int status;
 
 	usb_reset_configuration(d->udev);
 
@@ -1207,12 +1213,16 @@ static int lme2510_identify_state(struct dvb_usb_device *d, const char **name)
 
 	st->dvb_usb_lme2510_firmware = dvb_usb_lme2510_firmware;
 
-	if (lme2510_return_status(d) == 0x44) {
+	status = lme2510_return_status(d);
+	if (status == 0x44) {
 		*name = lme_firmware_switch(d, 0);
 		return COLD;
 	}
 
-	return 0;
+	if (status != 0x47)
+		return -EINVAL;
+
+	return WARM;
 }
 
 static int lme2510_get_stream_config(struct dvb_frontend *fe, u8 *ts_type,