[PATCH v3 3/3] vfio/pci: Check BAR resources before exporting a DMABUF

[Matt Evans <mattev@meta.com>]

A DMABUF exports access to BAR resources and, although they are
requested at startup time, we need to ensure they really were reserved
before exporting.  Otherwise, it's possible to access unreserved
resources through the export.

Add a check to the DMABUF-creation path.

Fixes: 5d74781ebc86c ("vfio/pci: Add dma-buf export support for MMIO regions")
Signed-off-by: Matt Evans <mattev@meta.com>
---
 drivers/vfio/pci/vfio_pci_dmabuf.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/vfio/pci/vfio_pci_dmabuf.c b/drivers/vfio/pci/vfio_pci_dmabuf.c
index f87fd32e4a01..3bc7d850e258 100644
--- a/drivers/vfio/pci/vfio_pci_dmabuf.c
+++ b/drivers/vfio/pci/vfio_pci_dmabuf.c
@@ -244,9 +244,11 @@ int vfio_pci_core_feature_dma_buf(struct vfio_pci_core_device *vdev, u32 flags,
 		return -EINVAL;
 
 	/*
-	 * For PCI the region_index is the BAR number like everything else.
+	 * For PCI the region_index is the BAR number like everything
+	 * else.  Check that PCI resources have been claimed for it.
 	 */
-	if (get_dma_buf.region_index >= VFIO_PCI_ROM_REGION_INDEX)
+	if (get_dma_buf.region_index >= VFIO_PCI_ROM_REGION_INDEX ||
+	    !IS_ERR(vfio_pci_core_get_iomap(vdev, get_dma_buf.region_index)))
 		return -ENODEV;
 
 	dma_ranges = memdup_array_user(&arg->dma_ranges, get_dma_buf.nr_ranges,
-- 
2.47.3