linux-kernel - Re: [PATCH] xen-pciback: fix up cleanup path when alloc fails

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Date:	Wed, 2 Dec 2015 10:35:16 +0000
From:	David Vrabel <david.vrabel@...rix.com>
To:	Doug Goldstein <cardoe@...doe.com>,
	<xen-devel@...ts.xenproject.org>
CC:	<linux-kernel@...r.kernel.org>, Bob Liu <bob.liu@...cle.com>,
	Paul Durrant <paul.durrant@...rix.com>,
	Wei Liu <wei.liu2@...rix.com>,
	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Jonathan Creekmore <jonathan.creekmore@...il.com>
Subject: Re: [PATCH] xen-pciback: fix up cleanup path when alloc fails

On 26/11/15 20:32, Doug Goldstein wrote:
> When allocating a pciback device fails, avoid the possibility of a
> use after free.

We should not require clearing drvdata for correctness.  We should
ensure we retain drvdata for as long as it is needed.

I note that pcistub_device_release() has:

	kfree(dev_data);
	pci_set_drvdata(dev, NULL);

	/* Clean-up the device */
	xen_pcibk_config_free_dyn_fields(dev);
	xen_pcibk_config_free_dev(dev);

Which should (at a minimum) be reordered to move the kfree(dev_data) to
after the calls that require it

David
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