USB: uss720 fixup refcount position

commit adaa3c6342b249548ea830fe8e02aa5b45be8688 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/misc/uss720.c b/drivers/usb/misc/uss720.c
index 4ff21587ab03214373364681a664df5d56a66a16..9727daa1cc724b036bdda4f84049d9a330810bc3 100644 (file)
--- 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;
 }