Re: [REGRESSION] 07ec51480b5e ("virtio_pci: use shared interrupts for virtqueues") causes crashes in guest

[Richard W.M. Jones]

On Thu, Mar 23, 2017 at 01:13:50PM +0800, Jason Wang wrote:
> >From 312859b596e83a2164a8430343d31fce2a5ad808 Mon Sep 17 00:00:00 2001
> From: Jason Wang <jasowang@xxxxxxxxxx>
> Date: Thu, 23 Mar 2017 13:07:16 +0800
> Subject: [PATCH] virtio_pci: fix out of bound access for msix_names
> 
> Signed-off-by: Jason Wang <jasowang@xxxxxxxxxx>

I tested this, and it does appear to fix the crashes in
vp_modern_find_vqs.  Therefore:

Tested-by: Richard W.M. Jones <rjones@xxxxxxxxxx>

Thanks,

Rich.

>  drivers/virtio/virtio_pci_common.c | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/virtio/virtio_pci_common.c b/drivers/virtio/virtio_pci_common.c
> index df548a6..5905349 100644
> --- a/drivers/virtio/virtio_pci_common.c
> +++ b/drivers/virtio/virtio_pci_common.c
> @@ -147,7 +147,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
>  {
>  	struct virtio_pci_device *vp_dev = to_vp_device(vdev);
>  	const char *name = dev_name(&vp_dev->vdev.dev);
> -	int i, err = -ENOMEM, allocated_vectors, nvectors;
> +	int i, j, err = -ENOMEM, allocated_vectors, nvectors;
>  	unsigned flags = PCI_IRQ_MSIX;
>  	bool shared = false;
>  	u16 msix_vec;
> @@ -212,7 +212,7 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
>  	if (!vp_dev->msix_vector_map)
>  		goto out_disable_config_irq;
>  
> -	allocated_vectors = 1; /* vector 0 is the config interrupt */
> +	allocated_vectors = j = 1; /* vector 0 is the config interrupt */
>  	for (i = 0; i < nvqs; ++i) {
>  		if (!names[i]) {
>  			vqs[i] = NULL;
> @@ -236,18 +236,19 @@ static int vp_find_vqs_msix(struct virtio_device *vdev, unsigned nvqs,
>  			continue;
>  		}
>  
> -		snprintf(vp_dev->msix_names[i + 1],
> +		snprintf(vp_dev->msix_names[j],
>  			 sizeof(*vp_dev->msix_names), "%s-%s",
>  			 dev_name(&vp_dev->vdev.dev), names[i]);
>  		err = request_irq(pci_irq_vector(vp_dev->pci_dev, msix_vec),
>  				  vring_interrupt, IRQF_SHARED,
> -				  vp_dev->msix_names[i + 1], vqs[i]);
> +				  vp_dev->msix_names[j], vqs[i]);
>  		if (err) {
>  			/* don't free this irq on error */
>  			vp_dev->msix_vector_map[i] = VIRTIO_MSI_NO_VECTOR;
>  			goto out_remove_vqs;
>  		}
>  		vp_dev->msix_vector_map[i] = msix_vec;
> +		j++;
>  
>  		/*
>  		 * Use a different vector for each queue if they are available,
> -- 
> 2.7.4
> 


-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html