iommu/vt-d: Fixed interaction of VFIO_IOMMU_MAP_DMA with IOMMU address limits

The BUG_ON in drivers/iommu/intel-iommu.c:785 can be triggered from userspace via
VFIO by calling the VFIO_IOMMU_MAP_DMA ioctl on a vfio device with any address
beyond the addressing capabilities of the IOMMU. The problem is that the ioctl code
calls iommu_iova_to_phys before it calls iommu_map. iommu_map handles the case that
it gets addresses beyond the addressing capabilities of its IOMMU.
intel_iommu_iova_to_phys does not.

This patch fixes iommu_iova_to_phys to return NULL for addresses beyond what the
IOMMU can handle. This in turn causes the ioctl call to fail in iommu_map and
(correctly) return EFAULT to the user with a helpful warning message in the kernel
log.

Signed-off-by: Julian Stecklina <jsteckli@os.inf.tu-dresden.de>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 15e9b57e9cf0..40203ada635e 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -782,7 +782,11 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain,
         int offset;
 
         BUG_ON(!domain->pgd);
-        BUG_ON(addr_width < BITS_PER_LONG && pfn >> addr_width);
+
+        if (addr_width < BITS_PER_LONG && pfn >> addr_width)
+                /* Address beyond IOMMU's addressing capabilities. */
+                return NULL;
+
         parent = domain->pgd;
 
         while (level > 0) {