Commit 45ba2154 authored Mar 06, 2015 by Aleksander Morgado Committed by Greg Kroah-Hartman Mar 06, 2015

xhci: fix reporting of 0-sized URBs in control endpoint

When a control transfer has a short data stage, the xHCI controller generates
two transfer events: a COMP_SHORT_TX event that specifies the untransferred
amount, and a COMP_SUCCESS event. But when the data stage is not short, only the
COMP_SUCCESS event occurs. Therefore, xhci-hcd must set urb->actual_length to
urb->transfer_buffer_length while processing the COMP_SUCCESS event, unless
urb->actual_length was set already by a previous COMP_SHORT_TX event.

The driver checks this by seeing whether urb->actual_length == 0, but this alone
is the wrong test, as it is entirely possible for a short transfer to have an
urb->actual_length = 0.

This patch changes the xhci driver to rely on a new td->urb_length_set flag,
which is set to true when a COMP_SHORT_TX event is received and the URB length
updated at that stage.

This fixes a bug which affected the HSO plugin, which relies on URBs with
urb->actual_length == 0 to halt re-submitting the RX URB in the control
endpoint.

Cc: <stable@vger.kernel.org>
Signed-off-by: Aleksander Morgado <aleksander@aleksander.es>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

parent d3d53894

drivers/usb/host/xhci-ring.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -1946,7 +1946,7 @@ static int process_ctrl_td(struct xhci_hcd xhci, struct xhci_td td,
		if (event_trb != ep_ring->dequeue) {
		/* The event was for the status stage */
		if (event_trb == td->last_trb) {
		if (td->urb->actual_length != 0) {
		if (td->urb_length_set) {
		/* Don't overwrite a previously set error code
		*/
		if ((status == -EINPROGRESS \|\| status == 0) &&
		@@ -1960,7 +1960,13 @@ static int process_ctrl_td(struct xhci_hcd xhci, struct xhci_td td,
		td->urb->transfer_buffer_length;
		}
		} else {
		/* Maybe the event was for the data stage? */
		/*
		* Maybe the event was for the data stage? If so, update
		* already the actual_length of the URB and flag it as
		* set, so that it is not overwritten in the event for
		* the last TRB.
		*/
		td->urb_length_set = true;
		td->urb->actual_length =
		td->urb->transfer_buffer_length -
		EVENT_TRB_LEN(le32_to_cpu(event->transfer_len));

drivers/usb/host/xhci.h

+3 −0

Original line number	Diff line number	Diff line

		/*
		* xHCI host controller driver
		*
		@@ -1291,6 +1292,8 @@ struct xhci_td {
		struct xhci_segment *start_seg;
		union xhci_trb *first_trb;
		union xhci_trb *last_trb;
		/* actual_length of the URB has already been set */
		bool urb_length_set;
		};

		/* xHCI command default timeout value */