linux-kernel - Re: [PATCH 1/2] virtio_pci: double free and invalid memory access of device vqs

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Date:	Sun, 4 Jan 2015 13:12:40 +0200
From:	"Michael S. Tsirkin" <mst@...hat.com>
To:	Sasha Levin <sasha.levin@...cle.com>
Cc:	linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>,
	"open list:VIRTIO CORE, NET..." 
	<virtualization@...ts.linux-foundation.org>
Subject: Re: [PATCH 1/2] virtio_pci: double free and invalid memory access of
 device vqs

On Fri, Jan 02, 2015 at 02:47:39PM -0500, Sasha Levin wrote:
> Device VQs were getting freed twice: once in every devices removal functions,
> and then again in virtio_pci_legacy_remove().
> 
> Signed-off-by: Sasha Levin <sasha.levin@...cle.com>

I see.  This used to be harmless because it used to be idempotent,
and safe to call any number of times.

I think your patch is right for 3.20:

Acked-by: Michael S. Tsirkin <mst@...hat.com>

but for 3.19 I'd prefer a more conservative approach of making
del_vqs idempotent again.

I'll post a patch like this shortly.


> ---
>  drivers/virtio/virtio_pci_legacy.c |    1 -
>  1 file changed, 1 deletion(-)
> 
> diff --git a/drivers/virtio/virtio_pci_legacy.c b/drivers/virtio/virtio_pci_legacy.c
> index 6c76f0f..913ca23 100644
> --- a/drivers/virtio/virtio_pci_legacy.c
> +++ b/drivers/virtio/virtio_pci_legacy.c
> @@ -298,7 +298,6 @@ void virtio_pci_legacy_remove(struct pci_dev *pci_dev)
>  
>  	unregister_virtio_device(&vp_dev->vdev);
>  
> -	vp_del_vqs(&vp_dev->vdev);
>  	pci_iounmap(pci_dev, vp_dev->ioaddr);
>  	pci_release_regions(pci_dev);
>  	pci_disable_device(pci_dev);
> -- 
> 1.7.10.4
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