Re: [PATCH net] ch9200: return error on failed register writes in ch9200_bind()

On 9/16/26 2:20 AM, netdev-bot+sashiko@kernel.org wrote:

Thank you for your contribution! Sashiko AI review found 1 potential
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Critical: 0 · High: 1 · Medium: 0 · Low: 0

- [High] Ineffective fix: the six newly added `if (retval < 0) return
  retval;` checks in ch9200_bind() (drivers/net/usb/ch9200.c) cannot…

--

ch9200: return error on failed register writes in ch9200_bind()

The patch adds error checks after the six control_write() calls in
ch9200_bind() so that a failed vendor register write aborts the bind
instead of being ignored.  It carries a Fixes tag for the original driver
commit 4a476bd6d1d9.

quoted

diff --git a/drivers/net/usb/ch9200.c b/drivers/net/usb/ch9200.c
index a206ffa76f1b9..ab3cd3902ed72 100644
--- a/drivers/net/usb/ch9200.c
+++ b/drivers/net/usb/ch9200.c

@@ -360,32 +360,44 @@ static int ch9200_bind(struct usbnet *dev, struct usb_interface *intf)
      data[1] = 0x0F;
      retval = control_write(dev, REQUEST_WRITE, 0, MAC_REG_THRESHOLD, data,
                             0x02, CONTROL_TIMEOUT_MS);
+     if (retval < 0)
+             return retval;

[Severity: High]

   But why? 8-)

Can these new checks ever observe a failed register write?  control_write()
in the same file discards the USB transfer status on its normal path:

   By "failed register write" I meant any error in control_write(), including
kmemdup() failure (which precludes the USB request from being sent at all)...

drivers/net/usb/ch9200.c:control_write() {
        ...
        err = usb_control_msg(dev->udev,
                              usb_sndctrlpipe(dev->udev, 0),
                              request, request_type, value, index, buf, size,
                              timeout);
        if (err >= 0 && err < size)
                err = -EINVAL;
        kfree(buf);

        return 0;

err_out:
        return err;
}

The only return err; is at err_out:, which is reached solely from the
kmemdup() -ENOMEM branch.  All six patched call sites pass a non-NULL
2-byte data buffer, so the only negative value the new checks can see is
-ENOMEM from that allocation.

   I kinda noticed. :-)

[...]

The sibling helper control_read() already returns err on its normal path,
and ch9200_mdio_read() checks it with if (ret < 0), so the convention
control_write() is expected to follow already exists in this file.

   And I'm extending it to control_write(), but in another patch...

Would it make more sense to change control_write() to return err after
kfree(buf) instead of (or in addition to) adding the caller-side checks?
As it stands the commit message claim that this makes the driver "bail out
of ch9200_bind() on failed writes" does not seem to hold for actual
transfer failures.

   I'm getting bored...
   If any *human* maintainer insists that I merge the 2 patches, I surely
will... Or maybe I should resubmit both against net.git (net-next.git?) as
a series?

[...]

MBR, Sergey