Commit 585df1d9 authored by Sarah Sharp's avatar Sarah Sharp
Browse files

xhci: Remove TDs from TD lists when URBs are canceled. 



When a driver tries to cancel an URB, and the host controller is dying,
xhci_urb_dequeue will giveback the URB without removing the xhci_tds
that comprise that URB from the td_list or the cancelled_td_list.  This
can cause a race condition between the driver calling URB dequeue and
the stop endpoint command watchdog timer.

If the timer fires on a dying host, and a driver attempts to resubmit
while the watchdog timer has dropped the xhci->lock to giveback a
cancelled URB, URBs may be given back by the xhci_urb_dequeue() function.
At that point, the URB's priv pointer will be freed and set to NULL, but
the TDs will remain on the td_list.  This will cause an oops in
xhci_giveback_urb_in_irq() when the watchdog timer attempts to loop
through the endpoints' td_lists, giving back killed URBs.

Make sure that xhci_urb_dequeue() removes TDs from the TD lists and
canceled TD lists before it gives back the URB.

This patch should be backported to kernels as old as 2.6.36.

Signed-off-by: default avatarSarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Andiry Xu <andiry.xu@amd.com>
Cc: stable@kernel.org
parent 522989a2

drivers/usb/host/xhci-ring.c

+8 −8
Original line number Diff line number Diff line
@@ -741,7 +741,7 @@ remove_finished_td: 
		 * so remove it from the endpoint ring's TD list.  Keep it in

		 * the cancelled TD list for URB completion later.

		 */

		list_del(&cur_td->td_list);

		list_del_init(&cur_td->td_list);

	}

	last_unlinked_td = cur_td;

	xhci_stop_watchdog_timer_in_irq(xhci, ep);
@@ -769,7 +769,7 @@ remove_finished_td: 
	do {

		cur_td = list_entry(ep->cancelled_td_list.next,

				struct xhci_td, cancelled_td_list);

		list_del(&cur_td->cancelled_td_list);

		list_del_init(&cur_td->cancelled_td_list);



		/* Clean up the cancelled URB */

		/* Doesn't matter what we pass for status, since the core will
@@ -877,9 +877,9 @@ void xhci_stop_endpoint_command_watchdog(unsigned long arg) 
				cur_td = list_first_entry(&ring->td_list,

						struct xhci_td,

						td_list);

				list_del(&cur_td->td_list);

				list_del_init(&cur_td->td_list);

				if (!list_empty(&cur_td->cancelled_td_list))

					list_del(&cur_td->cancelled_td_list);

					list_del_init(&cur_td->cancelled_td_list);

				xhci_giveback_urb_in_irq(xhci, cur_td,

						-ESHUTDOWN, "killed");

			}
@@ -888,7 +888,7 @@ void xhci_stop_endpoint_command_watchdog(unsigned long arg) 
						&temp_ep->cancelled_td_list,

						struct xhci_td,

						cancelled_td_list);

				list_del(&cur_td->cancelled_td_list);

				list_del_init(&cur_td->cancelled_td_list);

				xhci_giveback_urb_in_irq(xhci, cur_td,

						-ESHUTDOWN, "killed");

			}
@@ -1580,10 +1580,10 @@ td_cleanup: 
			else

				*status = 0;

		}

		list_del(&td->td_list);

		list_del_init(&td->td_list);

		/* Was this TD slated to be cancelled but completed anyway? */

		if (!list_empty(&td->cancelled_td_list))

			list_del(&td->cancelled_td_list);

			list_del_init(&td->cancelled_td_list);



		urb_priv->td_cnt++;

		/* Giveback the urb when all the tds are completed */
@@ -3362,7 +3362,7 @@ cleanup: 
	/* Clean up a partially enqueued isoc transfer. */



	for (i--; i >= 0; i--)

		list_del(&urb_priv->td[i]->td_list);

		list_del_init(&urb_priv->td[i]->td_list);



	/* Use the first TD as a temporary variable to turn the TDs we've queued

	 * into No-ops with a software-owned cycle bit. That way the hardware

drivers/usb/host/xhci.c

+7 −0
Original line number Diff line number Diff line
@@ -1252,6 +1252,13 @@ int xhci_urb_dequeue(struct usb_hcd *hcd, struct urb *urb, int status) 
	if (temp == 0xffffffff || (xhci->xhc_state & XHCI_STATE_HALTED)) {

		xhci_dbg(xhci, "HW died, freeing TD.\n");

		urb_priv = urb->hcpriv;

		for (i = urb_priv->td_cnt; i < urb_priv->length; i++) {

			td = urb_priv->td[i];

			if (!list_empty(&td->td_list))

				list_del_init(&td->td_list);

			if (!list_empty(&td->cancelled_td_list))

				list_del_init(&td->cancelled_td_list);

		}



		usb_hcd_unlink_urb_from_ep(hcd, urb);

		spin_unlock_irqrestore(&xhci->lock, flags);

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