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

[Paolo Abeni <pabeni@redhat.com>]

On 9/16/26 18:58, Sergey Shtylyov wrote:
> On 9/16/26 2:20 AM, netdev-bot+sashiko@kernel.org wrote:
> 
>> Thank you for your contribution! Sashiko AI review found 1 potential
>> issue(s) to consider:
>>
>> 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.
>>
>>> 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?
IMHO the patches are so strictly interconnected that should land into 
the same (net-next) series. No fixes tags in net-next patches.

Thanks,

Paolo