Re: [PATCH v2] usb: usbip: fix a refcount leak in stub_probe()

[Hangyu Hua]

On 2022/4/8 23:04, Shuah Khan wrote:
> On 4/7/22 7:59 PM, Hangyu Hua wrote:
> > Hi Shuah,
> >
> > I find this by code review. Do i really need to add this to commit 
> > log? This look like a little weird.
>
> Great. Good find.
>
> It is important to understand how the problem is found. Please add it
> the change log. We usually expect dmesg or such info. that revealed
> refcount leak, since this one is found during code review, we would
> like to see that information the commit log.
>
> Also please remember to avoid top posting.

I get what you meant now. But i don't know how to get a clear dmesg or 
any other log. The kernel will not crash because of this. I just used 
gdb to find that udev->dev->kobj->kref gets bigger and bigger whenever I 
call stub_probe with busid_priv->status = STUB_BUSID_REMOV.

Thanks for telling me the rules.

> > On 2022/4/8 00:31, Shuah Khan wrote:
> > > On 4/6/22 8:22 PM, Hangyu Hua wrote:
> > > > usb_get_dev() is called in stub_device_alloc(). When stub_probe() fails
> > > > after that, usb_put_dev() needs to be called to release the reference.
> > > >
> > > > Fix this by moving usb_put_dev() to sdev_free error path handling.
> > > >
> > > > Fixes: 3ff67445750a ("usbip: fix error handling in stub_probe()")
> > > > Signed-off-by: Hangyu Hua <hbh25y@xxxxxxxxx>
> > > > Reviewed-by: Shuah Khan <skhan@xxxxxxxxxxxxxxxxxxx>
> > > > ---
> > > >
> > > > v2: add more description of this patch.
> > >
> > > Still missing details on how this problem was found. Please add them
> > > to the commit log.
>
> thanks,
> -- Shuah