media: rtl28xxu: fix zero-length control request

The direction of the pipe argument must match the request-type direction
bit or control requests may fail depending on the host-controller-driver
implementation.

Control transfers without a data stage are treated as OUT requests by
the USB stack and should be using usb_sndctrlpipe(). Failing to do so
will now trigger a warning.

The driver uses a zero-length i2c-read request for type detection so
update the control-request code to use usb_sndctrlpipe() in this case.

Note that actually trying to read the i2c register in question does not
work as the register might not exist (e.g. depending on the demodulator)
as reported by Eero Lehtinen <debiangamer2@gmail.com>.

Reported-by: syzbot+faf11bbadc5a372564da@syzkaller.appspotmail.com
Reported-by: Eero Lehtinen <debiangamer2@gmail.com>
Tested-by: Eero Lehtinen <debiangamer2@gmail.com>
Fixes: d0f232e823 ("[media] rtl28xxu: add heuristic to detect chip type")
Cc: stable@vger.kernel.org      # 4.0
Cc: Antti Palosaari <crope@iki.fi>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

drivers/media/usb/dvb-usb-v2/rtl28xxu.c

@@ -37,7 +37,16 @@ static int rtl28xxu_ctrl_msg(struct dvb_usb_device *d, struct rtl28xxu_req *req)
 	} else {
 		/* read */
 		requesttype = (USB_TYPE_VENDOR | USB_DIR_IN);
-		pipe = usb_rcvctrlpipe(d->udev, 0);
+
+		/*
+		 * Zero-length transfers must use usb_sndctrlpipe() and
+		 * rtl28xxu_identify_state() uses a zero-length i2c read
+		 * command to determine the chip type.
+		 */
+		if (req->size)
+			pipe = usb_rcvctrlpipe(d->udev, 0);
+		else
+			pipe = usb_sndctrlpipe(d->udev, 0);
 	}
 
 	ret = usb_control_msg(d->udev, pipe, 0, requesttype, req->value,