Re: [PATCH] wifi: ath6kl: Check that the read operation returns a data length of 0

Greg KH
2024-08-25T08:34:04Z

On Sun, Aug 25, 2024 at 04:14:17PM +0800, Edward Adam Davis wrote:
> On Sun, 25 Aug 2024 09:25:37 +0200, Greg KH wrote:
> > > If the data length returned by the device is 0, the read operation
> > > should be considered a failure.
> > >
> > > Reported-and-tested-by: syzbot+92c6dd14aaa230be6855@syzkaller.appspotmail.com
> > > Signed-off-by: Edward Adam Davis <eadavis@qq.com>
> > > ---
> > > drivers/net/wireless/ath/ath6kl/usb.c | 3 +++
> > > 1 file changed, 3 insertions(+)
> > >
> > > diff --git a/drivers/net/wireless/ath/ath6kl/usb.c b/drivers/net/wireless/ath/ath6kl/usb.c
> > > index 5220809841a6..2a89bab81b24 100644
> > > --- a/drivers/net/wireless/ath/ath6kl/usb.c
> > > +++ b/drivers/net/wireless/ath/ath6kl/usb.c
> > > @@ -1034,6 +1034,9 @@ static int ath6kl_usb_bmi_read(struct ath6kl *ar, u8 *buf, u32 len)
> > > ath6kl_err("Unable to read the bmi data from the device: %d\n",
> > > ret);
> > > return ret;
> > > + } else {
> > > + ath6kl_err("Actual read the bmi data length is 0 from the device\n");
> > > + return -EIO;
> >
> > Close, but not quite there. ath6kl_usb_submit_ctrl_in() needs to verify
> > that the actual amount of data was read that was asked for. If a short
> > read happens (or a long one), then an error needs to propagate out, not
> > just 0. See the "note:" line in that function for what needs to be
> > properly checked.
> >
> > hope this helps,
> Thanks for your analysis.
> I have carefully read your analysis and I am not sure if the following
> understanding is appropriate:
> diff --git a/drivers/net/wireless/ath/ath6kl/usb.c b/drivers/net/wireless/ath/ath6kl/usb.c
> index 2a89bab81b24..35884316a8c8 100644
> --- a/drivers/net/wireless/ath/ath6kl/usb.c
> +++ b/drivers/net/wireless/ath/ath6kl/usb.c
> @@ -932,6 +932,15 @@ static int ath6kl_usb_submit_ctrl_in(struct ath6kl_usb *ar_usb,
>
> kfree(buf);

First off, this should be using usb_control_msg_send() instead of having
to roll their own buffer handling, right?

> + /* There are two types of read failure situations that need to be captured:
> + * 1. short read: ret < size && ret >= 0
> + * 2. long read: ret > size
> + * */
> + if (req == ATH6KL_USB_CONTROL_REQ_RECV_BMI_RESP && ret != size) {
> + ath6kl_warn("Actual read the data length is: %d, but input size is %d\n", ret, size);
> + return -EIO;
> + }

If you switch to usb_control_msg_send() this logic gets a lot simpler.
Perhaps do that instead?

If not, then you need to check for "short writes" or zero writes, see
the documentation for usb_control_msg() for what it returns. Your
comment is not correct here, there are 3 different return "states" that
you need to handle.

And why are you caring about what the req type is?

thanks,

greg k-h