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Date:   Wed, 21 Jul 2021 10:14:28 +0200
From:   Greg KH <gregkh@linuxfoundation.org>
To:     "Schmid, Carsten" <Carsten_Schmid@mentor.com>
Cc:     Mathias Nyman <mathias.nyman@linux.intel.com>,
        USB list <linux-usb@vger.kernel.org>
Subject: Re: Possible race in 4.14 xhci stack
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On Wed, Jul 21, 2021 at 07:51:58AM +0000, Schmid, Carsten wrote:
> Hi Greg,
> 
> >> Hi Mathias,
> >>
> >> i got a NULL pointer deref in the usbfs and analyzed it.
> >> The connected device seemed to have trouble on USB transmissions.
> >> However, I have the impression that there is a race between finishing URB handling and disconnection of devices.
> >> In detail:
> >> [ 4979.029666] xhci_hcd 0000:00:15.0: USB transfer error. Maybe the USB cable is bad?
> >
> > Did your cable die?
> >
> > And 4.14 is quite old, what about 5.13?
> >
> > thanks,
> >
> > greg k-h
> 
> That was reported from a device in the field.
> Yes, a defective cable is bad, but shouldn't the kernel's health avoid a NULL pointer deref?

Yes, I am not disagreeing about that, patches always welcome :)

thanks,

greg k-h