[PATCH 1/4] xhci: Set correct transferred length for cancelled bulk transfers

[Mathias Nyman <mathias.nyman@linux.intel.com>]

The transferred length is set incorrectly for cancelled bulk
transfer TDs in case the bulk transfer ring stops on the last transfer
block with a 'Stop - Length Invalid' completion code.

length essentially ends up being set to the requested length:
urb->actual_length = urb->transfer_buffer_length

Length for 'Stop - Length Invalid' cases should be the sum of all
TRB transfer block lengths up to the one the ring stopped on,
_excluding_ the one stopped on.

Fix this by always summing up TRB lengths for 'Stop - Length Invalid'
bulk cases.

This issue was discovered by Alan Stern while debugging
https://bugzilla.kernel.org/show_bug.cgi?id=218890, but does not
solve that bug. Issue is older than 4.10 kernel but fix won't apply
to those due to major reworks in that area.

Tested-by: Pierre Tomon <pierretom+12@ik.me>
Cc: stable@vger.kernel.org # v4.10+
Cc: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
---
 drivers/usb/host/xhci-ring.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/usb/host/xhci-ring.c b/drivers/usb/host/xhci-ring.c
index 9e90d2952760..1db61bb2b9b5 100644
--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -2524,9 +2524,8 @@ static int process_bulk_intr_td(struct xhci_hcd *xhci, struct xhci_virt_ep *ep,
 		goto finish_td;
 	case COMP_STOPPED_LENGTH_INVALID:
 		/* stopped on ep trb with invalid length, exclude it */
-		ep_trb_len	= 0;
-		remaining	= 0;
-		break;
+		td->urb->actual_length = sum_trb_lengths(xhci, ep_ring, ep_trb);
+		goto finish_td;
 	case COMP_USB_TRANSACTION_ERROR:
 		if (xhci->quirks & XHCI_NO_SOFT_RETRY ||
 		    (ep->err_count++ > MAX_SOFT_RETRY) ||
-- 
2.25.1