Re: [PATCH v3 1/2] usbip: give back URBs for unsent unlink requests during cleanup

[Shuah Khan]

On 8/17/21 11:39 PM, Greg KH wrote:
> On Tue, Aug 17, 2021 at 05:16:51PM -0600, Shuah Khan wrote:
> > On 8/13/21 12:25 PM, Anirudh Rayabharam wrote:
> > > In vhci_device_unlink_cleanup(), the URBs for unsent unlink requests are
> > > not given back. This sometimes causes usb_kill_urb to wait indefinitely
> > > for that urb to be given back. syzbot has reported a hung task issue [1]
> > > for this.
> > >
> > > To fix this, give back the urbs corresponding to unsent unlink requests
> > > (unlink_tx list) similar to how urbs corresponding to unanswered unlink
> > > requests (unlink_rx list) are given back.
> > >
> > > [1]: https://syzkaller.appspot.com/bug?id=08f12df95ae7da69814e64eb5515d5a85ed06b76
> > >
> > > Reported-by: syzbot+74d6ef051d3d2eacf428@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Tested-by: syzbot+74d6ef051d3d2eacf428@xxxxxxxxxxxxxxxxxxxxxxxxx
> > > Signed-off-by: Anirudh Rayabharam <mail@xxxxxxxxxxxxx>
> > > ---
> > >    drivers/usb/usbip/vhci_hcd.c | 26 ++++++++++++++++++++++++++
> > >    1 file changed, 26 insertions(+)
> > >
> > > diff --git a/drivers/usb/usbip/vhci_hcd.c b/drivers/usb/usbip/vhci_hcd.c
> > > index 4ba6bcdaa8e9..6f3f374d4bbc 100644
> > > --- a/drivers/usb/usbip/vhci_hcd.c
> > > +++ b/drivers/usb/usbip/vhci_hcd.c
> > > @@ -957,8 +957,34 @@ static void vhci_device_unlink_cleanup(struct vhci_device *vdev)
> > >    	spin_lock(&vdev->priv_lock);
> > >    	list_for_each_entry_safe(unlink, tmp, &vdev->unlink_tx, list) {
> > > +		struct urb *urb;
> > > +
> > > +		/* give back URB of unsent unlink request */
> > >    		pr_info("unlink cleanup tx %lu\n", unlink->unlink_seqnum);
> >
> > I know this is an exiting one.
> > Let's make this pr_debug or remove it all together.
> >
> > > +
> > > +		urb = pickup_urb_and_free_priv(vdev, unlink->unlink_seqnum);
> > > +		if (!urb) {
> > > +			pr_info("the urb (seqnum %lu) was already given back\n",
> > > +				unlink->unlink_seqnum);
> >
> > Let's make this pr_debug or remove it all together.
>
> As you have a struct device for all of these, please use dev_dbg() and
> friends, not pr_*(), for all of these.

Yes. Makes perfect sense.

thanks,
-- Shuah