4 files changed, 56 insertions, 3 deletions
diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index fc9018e..e1b4262 100644
--- a/drivers/usb/core/hcd.c
+++ b/drivers/usb/core/hcd.c
@@ -106,6 +106,9 @@ static DEFINE_SPINLOCK(hcd_root_hub_lock);
 /* used when updating an endpoint's URB list */
 static DEFINE_SPINLOCK(hcd_urb_list_lock);
 
+/* used to protect against unlinking URBs after the device is gone */
+static DEFINE_SPINLOCK(hcd_urb_unlink_lock);
+
 /* wait queue for synchronous unlinks */
 DECLARE_WAIT_QUEUE_HEAD(usb_kill_urb_queue);
 
@@ -1376,10 +1379,25 @@ static int unlink1(struct usb_hcd *hcd, struct urb *urb, int status)
 int usb_hcd_unlink_urb (struct urb *urb, int status)
 {
 	struct usb_hcd		*hcd;
-	int			retval;
+	int			retval = -EIDRM;
+	unsigned long		flags;
 
-	hcd = bus_to_hcd(urb->dev->bus);
-	retval = unlink1(hcd, urb, status);
+	/* Prevent the device and bus from going away while
+	 * the unlink is carried out.  If they are already gone
+	 * then urb->use_count must be 0, since disconnected
+	 * devices can't have any active URBs.
+	 */
+	spin_lock_irqsave(&hcd_urb_unlink_lock, flags);
+	if (atomic_read(&urb->use_count) > 0) {
+		retval = 0;
+		usb_get_dev(urb->dev);
+	}
+	spin_unlock_irqrestore(&hcd_urb_unlink_lock, flags);
+	if (retval == 0) {
+		hcd = bus_to_hcd(urb->dev->bus);
+		retval = unlink1(hcd, urb, status);
+		usb_put_dev(urb->dev);
+	}
 
 	if (retval == 0)
 		retval = -EINPROGRESS;
@@ -1528,6 +1546,17 @@ void usb_hcd_disable_endpoint(struct usb_device *udev,
 		hcd->driver->endpoint_disable(hcd, ep);
 }
 
+/* Protect against drivers that try to unlink URBs after the device
+ * is gone, by waiting until all unlinks for @udev are finished.
+ * Since we don't currently track URBs by device, simply wait until
+ * nothing is running in the locked region of usb_hcd_unlink_urb().
+ */
+void usb_hcd_synchronize_unlinks(struct usb_device *udev)
+{
+	spin_lock_irq(&hcd_urb_unlink_lock);
+	spin_unlock_irq(&hcd_urb_unlink_lock);
+}
+
 /*-------------------------------------------------------------------------*/
 
 /* called in any context */
diff --git a/drivers/usb/core/hcd.h b/drivers/usb/core/hcd.h
index 2dcde61..9465e70 100644
--- a/drivers/usb/core/hcd.h
+++ b/drivers/usb/core/hcd.h
@@ -232,6 +232,7 @@ extern void usb_hcd_flush_endpoint(struct usb_device *udev,
 		struct usb_host_endpoint *ep);
 extern void usb_hcd_disable_endpoint(struct usb_device *udev,
 		struct usb_host_endpoint *ep);
+extern void usb_hcd_synchronize_unlinks(struct usb_device *udev);
 extern int usb_hcd_get_frame_number(struct usb_device *udev);
 
 extern struct usb_hcd *usb_create_hcd(const struct hc_driver *driver,
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 9b3f16b..37ff8ae 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -1429,6 +1429,7 @@ void usb_disconnect(struct usb_device **pdev)
 	 */
 	dev_dbg (&udev->dev, "unregistering device\n");
 	usb_disable_device(udev, 0);
+	usb_hcd_synchronize_unlinks(udev);
 
 	usb_unlock_device(udev);
 
diff --git a/drivers/usb/core/urb.c b/drivers/usb/core/urb.c
index f263800..4342bd9 100644
--- a/drivers/usb/core/urb.c
+++ b/drivers/usb/core/urb.c
@@ -474,6 +474,12 @@ EXPORT_SYMBOL_GPL(usb_submit_urb);
  * indicating that the request has been canceled (rather than any other
  * code).
  *
+ * Drivers should not call this routine or related routines, such as
+ * usb_kill_urb() or usb_unlink_anchored_urbs(), after their disconnect
+ * method has returned.  The disconnect function should synchronize with
+ * a driver's I/O routines to insure that all URB-related activity has
+ * completed before it returns.
+ *
  * This request is always asynchronous.  Success is indicated by
  * returning -EINPROGRESS, at which time the URB will probably not yet
  * have been given back to the device driver.  When it is eventually
@@ -550,6 +556,9 @@ EXPORT_SYMBOL_GPL(usb_unlink_urb);
  * This routine may not be used in an interrupt context (such as a bottom
  * half or a completion handler), or when holding a spinlock, or in other
  * situations where the caller can't schedule().
+ *
+ * This routine should not be called by a driver after its disconnect
+ * method has returned.
  */
 void usb_kill_urb(struct urb *urb)
 {
@@ -588,6 +597,9 @@ EXPORT_SYMBOL_GPL(usb_kill_urb);
  * This routine may not be used in an interrupt context (such as a bottom
  * half or a completion handler), or when holding a spinlock, or in other
  * situations where the caller can't schedule().
+ *
+ * This routine should not be called by a driver after its disconnect
+ * method has returned.
  */
 void usb_poison_urb(struct urb *urb)
 {
@@ -622,6 +634,9 @@ EXPORT_SYMBOL_GPL(usb_unpoison_urb);
  *
  * this allows all outstanding URBs to be killed starting
  * from the back of the queue
+ *
+ * This routine should not be called by a driver after its disconnect
+ * method has returned.
  */
 void usb_kill_anchored_urbs(struct usb_anchor *anchor)
 {
@@ -651,6 +666,9 @@ EXPORT_SYMBOL_GPL(usb_kill_anchored_urbs);
  * this allows all outstanding URBs to be poisoned starting
  * from the back of the queue. Newly added URBs will also be
  * poisoned
+ *
+ * This routine should not be called by a driver after its disconnect
+ * method has returned.
  */
 void usb_poison_anchored_urbs(struct usb_anchor *anchor)
 {
@@ -672,6 +690,7 @@ void usb_poison_anchored_urbs(struct usb_anchor *anchor)
 	spin_unlock_irq(&anchor->lock);
 }
 EXPORT_SYMBOL_GPL(usb_poison_anchored_urbs);
+
 /**
  * usb_unlink_anchored_urbs - asynchronously cancel transfer requests en masse
  * @anchor: anchor the requests are bound to
@@ -680,6 +699,9 @@ EXPORT_SYMBOL_GPL(usb_poison_anchored_urbs);
  * from the back of the queue. This function is asynchronous.
  * The unlinking is just tiggered. It may happen after this
  * function has returned.
+ *
+ * This routine should not be called by a driver after its disconnect
+ * method has returned.
  */
 void usb_unlink_anchored_urbs(struct usb_anchor *anchor)
 {