1 files changed, 32 insertions, 3 deletions

diff --git a/drivers/usb/core/hcd.c b/drivers/usb/core/hcd.c
index fc9018e72a0..e1b42626d04 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 */