[PATCH v2 3/3] media: rtl28xxu: fix zero-length control request

Johan Hovold
2021-05-31T09:45:55Z

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: d0f232e823af ("[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>
---
drivers/media/usb/dvb-usb-v2/rtl28xxu.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c b/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
index 97ed17a141bb..a6124472cb06 100644
--- a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
+++ b/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,
--
2.31.1