dwc_otg: prevent OOPSes during device disconnects

The dwc_otg_urb_enqueue function is thread-unsafe. In particular the
access of urb->hcpriv, usb_hcd_link_urb_to_ep, dwc_otg_urb->qtd and
friends does not occur within a critical section and so if a device
was unplugged during activity there was a high chance that the
usbcore hub_thread would try to disable the endpoint with partially-
formed entries in the URB queue. This would result in BUG() or null
pointer dereferences.

Fix so that access of urb->hcpriv, enqueuing to the hardware and
adding to usbcore endpoint URB lists is contained within a single
critical section.

drivers/usb/host/dwc_otg/dwc_otg_hcd.c

@@ -464,7 +464,6 @@ int dwc_otg_hcd_urb_enqueue(dwc_otg_hcd_t * hcd,
 			    dwc_otg_hcd_urb_t * dwc_otg_urb, void **ep_handle,
 			    int atomic_alloc)
 {
-	dwc_irqflags_t flags;
 	int retval = 0;
 	uint8_t needs_scheduling = 0;
 	dwc_otg_transaction_type_e tr_type;
@@ -515,12 +514,10 @@ int dwc_otg_hcd_urb_enqueue(dwc_otg_hcd_t * hcd,
 	}
 
 	if(needs_scheduling) {
-		DWC_SPINLOCK_IRQSAVE(hcd->lock, &flags);
 		tr_type = dwc_otg_hcd_select_transactions(hcd);
 		if (tr_type != DWC_OTG_TRANSACTION_NONE) {
 			dwc_otg_hcd_queue_transactions(hcd, tr_type);
 		}
-		DWC_SPINUNLOCK_IRQRESTORE(hcd->lock, flags);
 	}
 	return retval;
 }

drivers/usb/host/dwc_otg/dwc_otg_hcd_linux.c

@@ -679,9 +679,7 @@ static int dwc_otg_urb_enqueue(struct usb_hcd *hcd,
 #if LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,28)
 	struct usb_host_endpoint *ep = urb->ep;
 #endif
-#if USB_URB_EP_LINKING
       	dwc_irqflags_t irqflags;
-#endif
         void **ref_ep_hcpriv = &ep->hcpriv;
 	dwc_otg_hcd_t *dwc_otg_hcd = hcd_to_dwc_otg_hcd(hcd);
 	dwc_otg_hcd_urb_t *dwc_otg_urb;
@@ -733,7 +731,6 @@ static int dwc_otg_urb_enqueue(struct usb_hcd *hcd,
 	if(dwc_otg_urb == NULL)
 		return -ENOMEM;
 
-	urb->hcpriv = dwc_otg_urb;
 	if (!dwc_otg_urb && urb->number_of_packets)
 		return -ENOMEM;
 
@@ -775,10 +772,10 @@ static int dwc_otg_urb_enqueue(struct usb_hcd *hcd,
 						    iso_frame_desc[i].length);
 	}
 
-#if USB_URB_EP_LINKING
 	DWC_SPINLOCK_IRQSAVE(dwc_otg_hcd->lock, &irqflags);
+	urb->hcpriv = dwc_otg_urb;
+#if USB_URB_EP_LINKING
 	retval = usb_hcd_link_urb_to_ep(hcd, urb);
-	DWC_SPINUNLOCK_IRQRESTORE(dwc_otg_hcd->lock, irqflags);
 	if (0 == retval)
 #endif
 	{
@@ -794,17 +791,16 @@ static int dwc_otg_urb_enqueue(struct usb_hcd *hcd,
 						urb);
 			}
 		} else {
-#if USB_URB_EP_LINKING
-			dwc_irqflags_t irqflags;
 			DWC_DEBUGPL(DBG_HCD, "DWC OTG dwc_otg_hcd_urb_enqueue failed rc %d\n", retval);
-			DWC_SPINLOCK_IRQSAVE(dwc_otg_hcd->lock, &irqflags);
+#if USB_URB_EP_LINKING
 			usb_hcd_unlink_urb_from_ep(hcd, urb);
-			DWC_SPINUNLOCK_IRQRESTORE(dwc_otg_hcd->lock, irqflags);
 #endif
+			urb->hcpriv = NULL;
 			if (retval == -DWC_E_NO_DEVICE)
 				retval = -ENODEV;
 		}
 	}
+	DWC_SPINUNLOCK_IRQRESTORE(dwc_otg_hcd->lock, irqflags);
 	return retval;
 }
 

drivers/usb/host/dwc_otg/dwc_otg_hcd_queue.c

@@ -919,6 +919,7 @@ void dwc_otg_hcd_qtd_init(dwc_otg_qtd_t * qtd, dwc_otg_hcd_urb_t * urb)
  * QH to place the QTD into.  If it does not find a QH, then it will create a
  * new QH. If the QH to which the QTD is added is not currently scheduled, it
  * is placed into the proper schedule based on its EP type.
+ * HCD lock must be held and interrupts must be disabled on entry
  *
  * @param[in] qtd The QTD to add
  * @param[in] hcd The DWC HCD structure
@@ -931,8 +932,6 @@ int dwc_otg_hcd_qtd_add(dwc_otg_qtd_t * qtd,
 			dwc_otg_hcd_t * hcd, dwc_otg_qh_t ** qh, int atomic_alloc)
 {
 	int retval = 0;
-	dwc_irqflags_t flags;
-
 	dwc_otg_hcd_urb_t *urb = qtd->urb;
 
 	/*
@@ -946,15 +945,12 @@ int dwc_otg_hcd_qtd_add(dwc_otg_qtd_t * qtd,
 			goto done;
 		}
 	}
-	DWC_SPINLOCK_IRQSAVE(hcd->lock, &flags);
 	retval = dwc_otg_hcd_qh_add(hcd, *qh);
 	if (retval == 0) {
 		DWC_CIRCLEQ_INSERT_TAIL(&((*qh)->qtd_list), qtd,
 					qtd_list_entry);
 		qtd->qh = *qh;
 	}
-	DWC_SPINUNLOCK_IRQRESTORE(hcd->lock, flags);
-
 done:
 
 	return retval;