USB: EHCI: bugfix: urb->hcpriv should not be NULL

commit 2656a9ab upstream.

This patch (as1632b) fixes a bug in ehci-hcd.  The USB core uses
urb->hcpriv to determine whether or not an URB is active; host
controller drivers are supposed to set this pointer to a non-NULL
value when an URB is queued.  However ehci-hcd sets it to NULL for
isochronous URBs, which defeats the check in usbcore.

In itself this isn't a big deal.  But people have recently found that
certain sequences of actions will cause the snd-usb-audio driver to
reuse URBs without waiting for them to complete.  In the absence of
proper checking by usbcore, the URBs get added to their endpoint list
twice.  This leads to list corruption and a system freeze.

The patch makes ehci-hcd assign a meaningful value to urb->hcpriv for
isochronous URBs.  Improving robustness always helps.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Reported-by: Artem S. Tashkinov <t.artem@lycos.com>
Reported-by: Christof Meerwald <cmeerw@cmeerw.org>
[bwh: Backported to 3.2:
 - Adjust context
 - Also use usb_pipetype() to work out whether we should call qh_put()]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Yang Yingliang <yangyingliang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-q.c

@@ -264,17 +264,13 @@ ehci_urb_done(struct ehci_hcd *ehci, struct urb *urb, int status)
 __releases(ehci->lock)
 __acquires(ehci->lock)
 {
-	if (likely (urb->hcpriv != NULL)) {
-		struct ehci_qh	*qh = (struct ehci_qh *) urb->hcpriv;
-
-		/* S-mask in a QH means it's an interrupt urb */
-		if ((qh->hw->hw_info2 & cpu_to_hc32(ehci, QH_SMASK)) != 0) {
-
-			/* ... update hc-wide periodic stats (for usbfs) */
+	if (usb_pipetype(urb->pipe) == PIPE_INTERRUPT) {
+		/* ... update hc-wide periodic stats */
 		ehci_to_hcd(ehci)->self.bandwidth_int_reqs--;
 	}
-		qh_put (qh);
-	}
+
+	if (usb_pipetype(urb->pipe) != PIPE_ISOCHRONOUS)
+		qh_put((struct ehci_qh *) urb->hcpriv);
 
 	if (unlikely(urb->unlinked)) {
 		COUNT(ehci->stats.unlink);

drivers/usb/host/ehci-sched.c

@@ -1684,7 +1684,7 @@ itd_link_urb (
 
 	/* don't need that schedule data any more */
 	iso_sched_free (stream, iso_sched);
-	urb->hcpriv = NULL;
+	urb->hcpriv = stream;
 
 	timer_action (ehci, TIMER_IO_WATCHDOG);
 	return enable_periodic(ehci);
@@ -2094,7 +2094,7 @@ sitd_link_urb (
 
 	/* don't need that schedule data any more */
 	iso_sched_free (stream, sched);
-	urb->hcpriv = NULL;
+	urb->hcpriv = stream;
 
 	timer_action (ehci, TIMER_IO_WATCHDOG);
 	return enable_periodic(ehci);