netdev - Re: [[PATCH stable <3.12]] xen-netback: fix refcnt unbalance for 3.11 and earlier versions

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Message-ID: <20131202120134.GA14293@zion.uk.xensource.com>
Date:	Mon, 2 Dec 2013 12:01:34 +0000
From:	Wei Liu <wei.liu2@...rix.com>
To:	Greg KH <gregkh@...uxfoundation.org>
CC:	Wei Liu <wei.liu2@...rix.com>, <xen-devel@...ts.xen.org>,
	<netdev@...r.kernel.org>, <stable@...r.kernel.org>,
	<tomasz.wroblewski@...rix.com>,
	Ian Campbell <ian.campbell@...rix.com>,
	Konrad Wilk <konrad.wilk@...cle.com>,
	David Vrabel <david.vrabel@...rix.com>
Subject: Re: [[PATCH stable <3.12]] xen-netback: fix refcnt unbalance for
 3.11 and earlier versions

On Sat, Nov 30, 2013 at 08:48:35PM -0800, Greg KH wrote:
> On Thu, Nov 28, 2013 at 12:48:09PM +0000, Wei Liu wrote:
> > With the introduction of "xen-netback: Don't destroy the netdev until
> > the vif is shut down" (upstream commit id 279f438e36), vif disconnect
> > and free are separated. However in the backported verion reference
> > counting code was not correctly modified, and the reset of vif->tx_irq
> > was lost. If frontend goes through vif life cycle more than once the
> > reference counting is skewed.
> > 
> > This patch adds back the missing tx_irq reset line. It also moves
> > several lines of the reference counting code to vif_free, so the moved
> > code corresponds to the counterpart in vif_alloc, thus the reference
> > counting is balanced.
> > 
> > 3.12 and onward versions are not affected by this bug, because reference
> > counting code was removed due to the introduction of 1:1 model.
> > 
> > This pacth should be backported to all stable verions which are lower
> > than 3.12 and have 279f438e36.
> 
> What stable versions are those?  279f438e36 showed up in 3.12-rc2, and
> was not marked for stable inclusion, so what kernel would end up needing
> this patch?
> 

Greg,

279f438e36 was backported to at least stable branches 

  3.11.y: <13826815042174@...ah.org> commit id f495ddc46
  3.10.y: <13828112161592@...ah.com> commit id a4626bf64

So at least those two need this patch.

And I remeber 3.8.y.z extended stable branch maintained by Kamal also
has the said commit.

> confused,
> 

Sorry, I should've stated cleared all versions.

BTW the above patch applies to 3.11.y. I can provide backports to 3.10.y
as well, if necessary.

Wei.

> greg k-h
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