[PATCH 4.7 121/184] xhci: fix null pointer dereference in stop command timeout function

[Greg Kroah-Hartman]

4.7-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>

commit bcf42aa60c2832510b9be0f30c090bfd35bb172d upstream.

The stop endpoint command has its own 5 second timeout timer.
If the timeout function is triggered between USB3 and USB2 host
removal it will try to call usb_hc_died(xhci_to_hcd(xhci)->primary_hcd)

the ->primary_hcd will be set to NULL at USB3 hcd removal.

Fix this by first checking if the PCI host is being removed, and
also by using only xhci_to_hcd() as it will always return the primary
hcd.

Signed-off-by: Mathias Nyman <mathias.nyman@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>

---
 drivers/usb/host/xhci-ring.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/usb/host/xhci-ring.c
+++ b/drivers/usb/host/xhci-ring.c
@@ -840,6 +840,10 @@ void xhci_stop_endpoint_command_watchdog
 	spin_lock_irqsave(&xhci->lock, flags);
 
 	ep->stop_cmds_pending--;
+	if (xhci->xhc_state & XHCI_STATE_REMOVING) {
+		spin_unlock_irqrestore(&xhci->lock, flags);
+		return;
+	}
 	if (xhci->xhc_state & XHCI_STATE_DYING) {
 		xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,
 				"Stop EP timer ran, but another timer marked "
@@ -893,7 +897,7 @@ void xhci_stop_endpoint_command_watchdog
 	spin_unlock_irqrestore(&xhci->lock, flags);
 	xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,
 			"Calling usb_hc_died()");
-	usb_hc_died(xhci_to_hcd(xhci)->primary_hcd);
+	usb_hc_died(xhci_to_hcd(xhci));
 	xhci_dbg_trace(xhci, trace_xhci_dbg_cancel_urb,
 			"xHCI host controller is dead.");
 }