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

[Edward Adam Davis <eadavis@qq.com>]

On Sun, 25 Aug 2024 13:25:56 +0200, Greg KH wrote:
> On Sun, Aug 25, 2024 at 06:09:45PM +0800, Edward Adam Davis wrote:
> > On Sun, 25 Aug 2024 10:34:00 +0200, Greg KH wrote:
> > > 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?
> > I couldn't figure it out with what you said. 
> 
> Meaning this kfree() should not be needed if you use
> usb_control_msg_send() (nor the allocation above it.)
> 
> > ath6kl_usb_submit_ctrl_in() is similar to usb_control_msg_send(),
> > both calling usb_control_msg() to communicate with USB devices.
> 
> Yes, it's close, but not quite the same.
> 
> > In the current issue, when executing an ATH6KL_USB_CONTROL_REQ_RECV_BMI_RESP
> > read request, the length of the data returned from the device is 0, which
> > is different from the expected length of the data to be read, resulting in
> > a warning.
> > 
> > ath6kl_usb_submit_ctrl_in()--->
> > 	usb_control_msg()--->
> > 		usb_internal_control_msg()
> > 
> > usb_internal_control_msg() will return the length of the data returned from
> > the device, usb_control_msg() return the length too, so in ath6kl_usb_submit_ctrl_in(),
> > we can filter out incorrect data lengths by judging the value of ret, such
> > as ret != Size situation.
> 
> Then just do that type of check for that type of read request in the
> code that does that call, not 2-3 layers deeper, no need for making this
> more complex than needed.
> 
> Try removing both of these functions and just call usb functions
> directly.
I have tried following fix:
diff --git a/drivers/net/wireless/ath/ath6kl/usb.c b/drivers/net/wireless/ath/ath6kl/usb.c
index 5220809841a6..dc1f89ebb740 100644
--- a/drivers/net/wireless/ath/ath6kl/usb.c
+++ b/drivers/net/wireless/ath/ath6kl/usb.c
@@ -1027,9 +1027,9 @@ static int ath6kl_usb_bmi_read(struct ath6kl *ar, u8 *buf, u32 len)
        int ret;
 
        /* get response */
-       ret = ath6kl_usb_submit_ctrl_in(ar_usb,
-                                       ATH6KL_USB_CONTROL_REQ_RECV_BMI_RESP,
-                                       0, 0, buf, len);
+       ret = usb_control_msg_recv(ar_usb->udev, 0, ATH6KL_USB_CONTROL_REQ_RECV_BMI_RESP,
+                                USB_DIR_IN | USB_TYPE_VENDOR |
+                                USB_RECIP_DEVICE, 0, 0, buf, len, 2000, GFP_KERNEL);
        if (ret) {
                ath6kl_err("Unable to read the bmi data from the device: %d\n",
                           ret);

I researched usb_control_msg_recv(), It handles the abnormal length of the
returned data, so using it directly can fix this warning.

BR,
Edward