Re: [PATCH v2] vfio/pci: Fix integer overflows, bitmask check

[Alex Williamson <alex.williamson@redhat.com>]

On Wed, 12 Oct 2016 09:53:49 +0200
Vlad Tsyrklevich <vlad@tsyrklevich.net> wrote:

> The VFIO_DEVICE_SET_IRQS ioctl did not sufficiently sanitize
> user-supplied integers, potentially allowing arbitrary memory writes.
> This patch adds appropriate integer checks, and also verifies that only
> a single element in the VFIO_IRQ_SET_DATA_TYPE_MASK bitmask is set.
> VFIO_IRQ_SET_ACTION_TYPE_MASK is already correctly checked later in
> vfio_pci_set_irqs_ioctl().
> 
> Signed-off-by: Vlad Tsyrklevich <vlad@tsyrklevich.net>
> ---
>  drivers/vfio/pci/vfio_pci.c       | 26 +++++++++++++++++---------
>  drivers/vfio/pci/vfio_pci_intrs.c |  2 +-
>  2 files changed, 18 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci.c b/drivers/vfio/pci/vfio_pci.c
> index d624a52..44de13c 100644
> --- a/drivers/vfio/pci/vfio_pci.c
> +++ b/drivers/vfio/pci/vfio_pci.c
> @@ -829,6 +829,7 @@ static long vfio_pci_ioctl(void *device_data,
>  
>  	} else if (cmd == VFIO_DEVICE_SET_IRQS) {
>  		struct vfio_irq_set hdr;
> +		size_t size;
>  		u8 *data = NULL;
>  		int ret = 0;
>  
> @@ -838,20 +839,27 @@ static long vfio_pci_ioctl(void *device_data,
>  			return -EFAULT;
>  
>  		if (hdr.argsz < minsz || hdr.index >= VFIO_PCI_NUM_IRQS ||
> +		    hdr.count >= (U32_MAX - hdr.start) ||
>  		    hdr.flags & ~(VFIO_IRQ_SET_DATA_TYPE_MASK |
>  				  VFIO_IRQ_SET_ACTION_TYPE_MASK))
>  			return -EINVAL;
>  
> -		if (!(hdr.flags & VFIO_IRQ_SET_DATA_NONE)) {
> -			size_t size;
> -			int max = vfio_pci_get_irq_count(vdev, hdr.index);
> +		switch (hdr.flags & VFIO_IRQ_SET_DATA_TYPE_MASK) {
> +		case VFIO_IRQ_SET_DATA_NONE:
> +			size = 0;
> +			break;
> +		case VFIO_IRQ_SET_DATA_BOOL:
> +			size = sizeof(uint8_t);
> +			break;
> +		case VFIO_IRQ_SET_DATA_EVENTFD:
> +			size = sizeof(int32_t);
> +			break;
> +		default:
> +			return -EINVAL;
> +		}
>  
> -			if (hdr.flags & VFIO_IRQ_SET_DATA_BOOL)
> -				size = sizeof(uint8_t);
> -			else if (hdr.flags & VFIO_IRQ_SET_DATA_EVENTFD)
> -				size = sizeof(int32_t);
> -			else
> -				return -EINVAL;
> +		if (size) {
> +			int max = vfio_pci_get_irq_count(vdev, hdr.index);


Why not pull this out too so we can fully validate start/count for the
DATA_NONE case?

>  
>  			if (hdr.argsz - minsz < hdr.count * size ||
>  			    hdr.start >= max || hdr.start + hdr.count > max)
> diff --git a/drivers/vfio/pci/vfio_pci_intrs.c b/drivers/vfio/pci/vfio_pci_intrs.c
> index c2e6089..1c46045 100644
> --- a/drivers/vfio/pci/vfio_pci_intrs.c
> +++ b/drivers/vfio/pci/vfio_pci_intrs.c
> @@ -256,7 +256,7 @@ static int vfio_msi_enable(struct vfio_pci_device *vdev, int nvec, bool msix)
>  	if (!is_irq_none(vdev))
>  		return -EINVAL;
>  
> -	vdev->ctx = kzalloc(nvec * sizeof(struct vfio_pci_irq_ctx), GFP_KERNEL);
> +	vdev->ctx = kcalloc(nvec, sizeof(struct vfio_pci_irq_ctx), GFP_KERNEL);
>  	if (!vdev->ctx)
>  		return -ENOMEM;

Unrelated change?