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    SubjectRe: [PATCH 2/2] usbip: Fix error path of vhci_recv_ret_submit()
    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@invisiblethingslab.com>
    > Signed-off-by: Suwan Kim <suwan.kim027@gmail.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).

    Alan Stern

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