USB: uss720 fixup refcount position

My testprog do a lot of bitbang - after hours i got following warning and my machine lockups:
WARNING: at /build/buildd/linux-2.6.38/lib/kref.c:34
After debugging uss720 driver i discovered that the completion callback was called before
usb_submit_urb returns. The callback frees the request structure that is krefed on return by
usb_submit_urb.

Signed-off-by: Peter Holik <peter@holik.at>
Acked-by: Thomas Sailer <t.sailer@alumni.ethz.ch>
Cc: stable <stable@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 3 insertions, 4 deletions

diff --git a/drivers/usb/misc/uss720.c b/drivers/usb/misc/uss720.c
index f7a205738032..8b1d94a76914 100644
--- a/drivers/usb/misc/uss720.c
+++ b/drivers/usb/misc/uss720.c
@@ -177,12 +177,11 @@ static struct uss720_async_request *submit_async_request(struct parport_uss720_p
         spin_lock_irqsave(&priv->asynclock, flags);
         list_add_tail(&rq->asynclist, &priv->asynclist);
         spin_unlock_irqrestore(&priv->asynclock, flags);
+        kref_get(&rq->ref_count);
         ret = usb_submit_urb(rq->urb, mem_flags);
-        if (!ret) {
-                kref_get(&rq->ref_count);
+        if (!ret)
                 return rq;
-        }
-        kref_put(&rq->ref_count, destroy_async);
+        destroy_async(&rq->ref_count);
         err("submit_async_request submit_urb failed with %d", ret);
         return NULL;
 }