From: Julian Stecklina <jsteckli@os.info.tu-dresden.de>

Subject: [PATCH] vfio, iommu: 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>

---

 drivers/iommu/intel-iommu.c | 6 +++++-

 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c

index eec0d3e..61303db 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) {

-- 

1.8.3.1