linux-kernel - Re: [Xen-devel] [PATCH 26/38] xen: xenbus: add missing put

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Message-ID: <1389002445.13274.23.camel@kazak.uk.xensource.com>
Date:	Mon, 6 Jan 2014 10:00:45 +0000
From:	Ian Campbell <Ian.Campbell@...rix.com>
To:	David Vrabel <david.vrabel@...rix.com>
CC:	Levente Kurusa <levex@...ux.com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	<xen-devel@...ts.xenproject.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [Xen-devel] [PATCH 26/38] xen: xenbus: add missing put_device
 call

On Thu, 2014-01-02 at 13:53 +0000, David Vrabel wrote:
> On 19/12/13 15:03, Levente Kurusa wrote:
> > This is required so that we give up the last reference to the device.
> > 
> > Signed-off-by: Levente Kurusa <levex@...ux.com>
> > ---
> >  drivers/xen/xenbus/xenbus_probe.c | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/xen/xenbus/xenbus_probe.c b/drivers/xen/xenbus/xenbus_probe.c
> > index 3c0a74b..4abb9ee 100644
> > --- a/drivers/xen/xenbus/xenbus_probe.c
> > +++ b/drivers/xen/xenbus/xenbus_probe.c
> > @@ -465,8 +465,10 @@ int xenbus_probe_node(struct xen_bus_type *bus,
> >  
> >  	/* Register with generic device framework. */
> >  	err = device_register(&xendev->dev);
> > -	if (err)
> > +	if (err) {
> > +		put_device(&xendev->dev);
> >  		goto fail;
> > +	}
> >  
> >  	return 0;
> >  fail:
> 
> There is a kfree(xendev) here so this introduces a double-free.

How? put_device doesn't touch xendev itself, does it? It just drops the
ref on the dev member which is not separately dynamically allocated and
so not freed either.

Ian.


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