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.

Fix the zero-length i2c-read request used for type detection by
attempting to read a single byte instead.

Reported-by: syzbot+faf11bbadc5a372564da@syzkaller.appspotmail.com
Fixes: d0f232e8 ("[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: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

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

@@ -612,8 +612,9 @@ static int rtl28xxu_read_config(struct dvb_usb_device *d)
 static int rtl28xxu_identify_state(struct dvb_usb_device *d, const char **name)
 {
 	struct rtl28xxu_dev *dev = d_to_priv(d);
+	u8 buf[1];
 	int ret;
-	struct rtl28xxu_req req_demod_i2c = {0x0020, CMD_I2C_DA_RD, 0, NULL};
+	struct rtl28xxu_req req_demod_i2c = {0x0020, CMD_I2C_DA_RD, 1, buf};
 
 	dev_dbg(&d->intf->dev, "\n");