linux-kernel - Re: [PATCH] USB: EHCI: fix for leaking isochronous data

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Message-Id: <201303211910.31473.arnd@arndb.de>
Date:	Thu, 21 Mar 2013 19:10:31 +0000
From:	Arnd Bergmann <arnd@...db.de>
To:	Jason Cooper <jason@...edaemon.net>
Cc:	Soeren Moch <smoch@....de>, Alan Stern <stern@...land.harvard.edu>,
	USB list <linux-usb@...r.kernel.org>,
	Andrew Lunn <andrew@...n.ch>,
	Sebastian Hesselbarth <sebastian.hesselbarth@...il.com>,
	linux-mm@...ck.org,
	Kernel development list <linux-kernel@...r.kernel.org>,
	linux-arm-kernel@...ts.infradead.org, michael@...rulasolutions.com
Subject: Re: [PATCH] USB: EHCI: fix for leaking isochronous data

On Thursday 21 March 2013, Jason Cooper wrote:
> On Thu, Mar 21, 2013 at 06:04:59PM +0100, Soeren Moch wrote:

> > 
> > Now I found out what is going on here:
> > 
> > In itd_urb_transaction() we allocate 9 iTDs for each URB with
> > number_of_packets == 64 in my case. The iTDs are added to
> > sched->td_list. For a frame-aligned scheduling we need 8 iTDs, the
> > 9th one is released back to the front of the streams free_list in
> > iso_sched_free(). This iTD was cleared after allocation and has a
> > frame number of 0 now. So for each allocation when now_frame == 0 we
> > allocate from the dma_pool, not from the free_list. The attached
> > patch invalidates the frame number in each iTD before it is sent to
> > the scheduler. This fixes the problem without the need to iterate
> > over a iTD list.
> > 
> > Signed-off-by: Soeren Moch <smoch@....de>
> 
> Wow!  Great work Soeren!  Talk about a long road to a small fix.  Thanks
> for keeping after it.

+1

I hardly understand half of the description above, but that much sounds
plausible. Is this a bug fix that should get backported to stable kernels?

	Arnd
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