linux-kernel - [PATCH] [235/275] USB: uss720 fixup refcount position

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Message-Id: <20110330210801.236473E1A05@tassilo.jf.intel.com>
Date:	Wed, 30 Mar 2011 14:08:01 -0700 (PDT)
From:	Andi Kleen <andi@...stfloor.org>
To:	peter@...ik.at, t.sailer@...mni.ethz.ch, gregkh@...e.de,
	ak@...ux.intel.com, linux-kernel@...r.kernel.org,
	stable@...nel.org, tim.bird@...sony.com
Subject: [PATCH] [235/275] USB: uss720 fixup refcount position

2.6.35-longterm review patch.  If anyone has any objections, please let me know.

------------------
From: Peter Holik <peter@...ik.at>

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@...ik.at>
Acked-by: Thomas Sailer <t.sailer@...mni.ethz.ch>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>

---
 drivers/usb/misc/uss720.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

Index: linux-2.6.35.y/drivers/usb/misc/uss720.c
===================================================================
--- linux-2.6.35.y.orig/drivers/usb/misc/uss720.c	2011-03-29 22:50:20.427735723 -0700
+++ linux-2.6.35.y/drivers/usb/misc/uss720.c	2011-03-29 23:53:41.596473326 -0700
@@ -177,12 +177,11 @@
 	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;
 }
--
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