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

Edward Adam Davis
2024-08-25T08:27:50Z

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);

+ /* 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;
+ }
+
return 0;
}

BR,
Edward