linux-kernel - Re: [PATCH 3/3] media: rtl28xxu: fix zero-length control request

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Date:   Mon, 31 May 2021 09:55:39 +0200
From:   Johan Hovold <johan@...nel.org>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     Hans Verkuil <hverkuil@...all.nl>, linux-media@...r.kernel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        syzbot+faf11bbadc5a372564da@...kaller.appspotmail.com,
        stable@...r.kernel.org, Antti Palosaari <crope@....fi>
Subject: Re: [PATCH 3/3] media: rtl28xxu: fix zero-length control request

On Mon, May 24, 2021 at 01:09:20PM +0200, Johan Hovold wrote:
> 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@...kaller.appspotmail.com
> Fixes: d0f232e823af ("[media] rtl28xxu: add heuristic to detect chip type")
> Cc: stable@...r.kernel.org      # 4.0
> Cc: Antti Palosaari <crope@....fi>
> Signed-off-by: Johan Hovold <johan@...nel.org>
> ---
>  drivers/media/usb/dvb-usb-v2/rtl28xxu.c | 3 ++-
>  1 file changed, 2 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..2c04ed8af0e4 100644
> --- a/drivers/media/usb/dvb-usb-v2/rtl28xxu.c
> +++ b/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");

As reported here

	https://lore.kernel.org/r/YLSVsrhMZ2oOL1vM@hovoldconsulting.com

this patch is causing the chip type to no longer be detected correctly,
so please drop this one for now until this has been resolved.

Johan