[Linaro-mm-sig] Re: [PATCH v5 9/9] vfio/pci: Add dma-buf export support for MMIO regions

On Fri, Oct 17, 2025 at 10:02:49AM -0300, Jason Gunthorpe wrote:

On Mon, Oct 13, 2025 at 06:26:11PM +0300, Leon Romanovsky wrote:

...

+static void dma_ranges_to_p2p_phys(struct vfio_pci_dma_buf *priv,

• 		   struct vfio_device_feature_dma_buf *dma_buf,
  

• 		   struct vfio_region_dma_range *dma_ranges,
  

• 		   struct p2pdma_provider *provider)
  

+{

• struct pci_dev *pdev = priv->vdev->pdev;
• phys_addr_t pci_start;
• u32 i;
• pci_start = pci_resource_start(pdev, dma_buf->region_index);
• for (i = 0; i < dma_buf->nr_ranges; i++) {

• priv->phys_vec[i].len = dma_ranges[i].length;
  

• priv->phys_vec[i].paddr = pci_start + dma_ranges[i].offset;
  

• priv->size += priv->phys_vec[i].len;
  

• }

This is missing validation, the userspace can pass in any length/offset but the resource is of limited size. Like this:

static int dma_ranges_to_p2p_phys(struct vfio_pci_dma_buf *priv, struct vfio_device_feature_dma_buf *dma_buf, struct vfio_region_dma_range *dma_ranges, struct p2pdma_provider *provider) { struct pci_dev *pdev = priv->vdev->pdev; phys_addr_t len = pci_resource_len(pdev, dma_buf->region_index); phys_addr_t pci_start; phys_addr_t pci_last; u32 i;

if (!len) return -EINVAL; pci_start = pci_resource_start(pdev, dma_buf->region_index); pci_last = pci_start + len - 1; for (i = 0; i < dma_buf->nr_ranges; i++) { phys_addr_t last;

if (!dma_ranges[i].length)
	return -EINVAL;

if (check_add_overflow(pci_start, dma_ranges[i].offset,
		       &priv->phys_vec[i].paddr) ||
    check_add_overflow(priv->phys_vec[i].paddr,
		       dma_ranges[i].length - 1, &last))
	return -EOVERFLOW;
if (last > pci_last)
	return -EINVAL;

priv->phys_vec[i].len = dma_ranges[i].length;
priv->size += priv->phys_vec[i].len;

} priv->nr_ranges = dma_buf->nr_ranges; priv->provider = provider; return 0; }

I have these checks in validate_dmabuf_input(). Do you think that I need to add extra checks?

Thanks

Jason