linux-kernel - Re: [PATCH 2/2] usbip: Fix error path of vhci_recv_ret

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Date:   Fri, 13 Dec 2019 11:03:17 +0900
From:   Suwan Kim <suwan.kim027@...il.com>
To:     Alan Stern <stern@...land.harvard.edu>
Cc:     shuah@...nel.org, valentina.manea.m@...il.com,
        gregkh@...uxfoundation.org, marmarek@...isiblethingslab.com,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        stable@...r.kernel.org
Subject: Re: [PATCH 2/2] usbip: Fix error path of vhci_recv_ret_submit()

On Thu, Dec 12, 2019 at 10:54:08AM -0500, Alan Stern wrote:
> On Thu, 12 Dec 2019, Suwan Kim wrote:
> 
> > If a transaction error happens in vhci_recv_ret_submit(), event
> > handler closes connection and changes port status to kick hub_event.
> > Then hub tries to flush the endpoint URBs, but that causes infinite
> > loop between usb_hub_flush_endpoint() and vhci_urb_dequeue() because
> > "vhci_priv" in vhci_urb_dequeue() was already released by
> > vhci_recv_ret_submit() before a transmission error occurred. Thus,
> > vhci_urb_dequeue() terminates early and usb_hub_flush_endpoint()
> > continuously calls vhci_urb_dequeue().
> > 
> > The root cause of this issue is that vhci_recv_ret_submit()
> > terminates early without giving back URB when transaction error
> > occurs in vhci_recv_ret_submit(). That causes the error URB to still
> > be linked at endpoint list without “vhci_priv".
> > 
> > So, in the case of trasnaction error in vhci_recv_ret_submit(),
> > unlink URB from the endpoint, insert proper error code in
> > urb->status and give back URB.
> > 
> > Reported-by: Marek Marczykowski-Górecki <marmarek@...isiblethingslab.com>
> > Signed-off-by: Suwan Kim <suwan.kim027@...il.com>
> > ---
> >  drivers/usb/usbip/vhci_rx.c | 13 +++++++++----
> >  1 file changed, 9 insertions(+), 4 deletions(-)
> > 
> > diff --git a/drivers/usb/usbip/vhci_rx.c b/drivers/usb/usbip/vhci_rx.c
> > index 33f8972ba842..dc26acad6baf 100644
> > --- a/drivers/usb/usbip/vhci_rx.c
> > +++ b/drivers/usb/usbip/vhci_rx.c
> > @@ -77,16 +77,21 @@ static void vhci_recv_ret_submit(struct vhci_device *vdev,
> >  	usbip_pack_pdu(pdu, urb, USBIP_RET_SUBMIT, 0);
> >  
> >  	/* recv transfer buffer */
> > -	if (usbip_recv_xbuff(ud, urb) < 0)
> > -		return;
> > +	if (usbip_recv_xbuff(ud, urb) < 0) {
> > +		urb->status = -EPIPE;
> > +		goto error;
> > +	}
> >  
> >  	/* recv iso_packet_descriptor */
> > -	if (usbip_recv_iso(ud, urb) < 0)
> > -		return;
> > +	if (usbip_recv_iso(ud, urb) < 0) {
> > +		urb->status = -EPIPE;
> > +		goto error;
> > +	}
> 
> -EPIPE is used for STALL.  The appropriate error code for transaction 
> error would be -EPROTO (or -EILSEQ or -ETIME, but people seem to be 
> settling on -EPROTO).

Thanks for the feedback. I will fix it :)

Regards,
Suwan Kim