usb: wusbcore: prevent urb dequeue and giveback race

This patch takes a reference to the wa_xfer object in wa_urb_dequeue to
prevent the urb giveback code from completing the xfer and freeing it
while wa_urb_dequeue is executing.  It also checks for done at the start
to avoid a double completion scenario.  Adding the check for done in
urb_dequeue means that any other place where a submitted transfer
segment is marked as done must complete the transfer if it is done.
__wa_xfer_delayed_run was not checking this case so that check was added
as well.

Signed-off-by: Thomas Pugliese <thomas.pugliese@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 27 insertions, 10 deletions

diff --git a/drivers/usb/wusbcore/wa-xfer.c b/drivers/usb/wusbcore/wa-xfer.c
index cb061915f051..5e5343e69915 100644
--- a/drivers/usb/wusbcore/wa-xfer.c
+++ b/drivers/usb/wusbcore/wa-xfer.c
@@ -1471,6 +1471,8 @@ static int __wa_xfer_delayed_run(struct wa_rpipe *rpipe, int *dto_waiting)
                         xfer, wa_xfer_id(xfer), seg->index,
                         atomic_read(&rpipe->segs_available), result);
                 if (unlikely(result < 0)) {
+                        int done;
+
                         spin_unlock_irqrestore(&rpipe->seg_lock, flags);
                         spin_lock_irqsave(&xfer->lock, flags);
                         __wa_xfer_abort(xfer);
@@ -1479,7 +1481,10 @@ static int __wa_xfer_delayed_run(struct wa_rpipe *rpipe, int *dto_waiting)
                          * the RPIPE seg_list.  Mark it done.
                          */
                         xfer->segs_done++;
+                        done = __wa_xfer_is_done(xfer);
                         spin_unlock_irqrestore(&xfer->lock, flags);
+                        if (done)
+                                wa_xfer_completion(xfer);
                         spin_lock_irqsave(&rpipe->seg_lock, flags);
                 }
                 wa_xfer_put(xfer);
@@ -1915,20 +1920,20 @@ int wa_urb_dequeue(struct wahc *wa, struct urb *urb, int status)
         /* check if it is safe to unlink. */
         spin_lock_irqsave(&wa->xfer_list_lock, flags);
         result = usb_hcd_check_unlink_urb(&(wa->wusb->usb_hcd), urb, status);
+        if ((result == 0) && urb->hcpriv) {
+                /*
+                 * Get a xfer ref to prevent a race with wa_xfer_giveback
+                 * cleaning up the xfer while we are working with it.
+                 */
+                wa_xfer_get(urb->hcpriv);
+        }
         spin_unlock_irqrestore(&wa->xfer_list_lock, flags);
         if (result)
                 return result;
 
         xfer = urb->hcpriv;
-        if (xfer == NULL) {
-                /*
-                 * Nothing setup yet enqueue will see urb->status !=
-                 * -EINPROGRESS (by hcd layer) and bail out with
-                 * error, no need to do completion
-                 */
-                BUG_ON(urb->status == -EINPROGRESS);
-                goto out;
-        }
+        if (xfer == NULL)
+                return -ENOENT;
         spin_lock_irqsave(&xfer->lock, flags);
         pr_debug("%s: DEQUEUE xfer id 0x%08X\n", __func__, wa_xfer_id(xfer));
         rpipe = xfer->ep->hcpriv;
@@ -1939,6 +1944,16 @@ int wa_urb_dequeue(struct wahc *wa, struct urb *urb, int status)
                 result = -ENOENT;
                 goto out_unlock;
         }
+        /*
+         * Check for done to avoid racing with wa_xfer_giveback and completing
+         * twice.
+         */
+        if (__wa_xfer_is_done(xfer)) {
+                pr_debug("%s: xfer %p id 0x%08X already done.\n", __func__,
+                        xfer, wa_xfer_id(xfer));
+                result = -ENOENT;
+                goto out_unlock;
+        }
         /* Check the delayed list -> if there, release and complete */
         spin_lock_irqsave(&wa->xfer_list_lock, flags2);
         if (!list_empty(&xfer->list_node) && xfer->seg == NULL)
@@ -2007,11 +2022,12 @@ int wa_urb_dequeue(struct wahc *wa, struct urb *urb, int status)
                 wa_xfer_completion(xfer);
         if (rpipe_ready)
                 wa_xfer_delayed_run(rpipe);
+        wa_xfer_put(xfer);
         return result;
 
 out_unlock:
         spin_unlock_irqrestore(&xfer->lock, flags);
-out:
+        wa_xfer_put(xfer);
         return result;
 
 dequeue_delayed:
@@ -2020,6 +2036,7 @@ dequeue_delayed:
         xfer->result = urb->status;
         spin_unlock_irqrestore(&xfer->lock, flags);
         wa_xfer_giveback(xfer);
+        wa_xfer_put(xfer);
         usb_put_urb(urb);               /* we got a ref in enqueue() */
         return 0;
 }