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: Sarah Sharp <sarah.a.sharp@linux.intel.com>
Cc: Andiry Xu <andiry.xu@amd.com>
Cc: stable@kernel.org

1 files changed, 7 insertions, 0 deletions

diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c
index 8e84acff1134..3a0f695138f4 100644
--- a/drivers/usb/host/xhci.c
+++ b/drivers/usb/host/xhci.c
@@ -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);