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:

quoted

On Sun, 25 Aug 2024 09:25:37 +0200, Greg KH wrote:

quoted

quoted

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 <redacted>
---
 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. 

ath6kl_usb_submit_ctrl_in() is similar to usb_control_msg_send(),
both calling usb_control_msg() to communicate with USB devices.

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.

quoted

+       /* 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?

BR,
Edward