[PATCH 3.4 29/32] iommu/vt-d: Fixed interaction of VFIO_IOMMU_MAP_DMA with IOMMU address limits

Greg Kroah-Hartman
2013-12-06T21:54:31Z

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

commit f9423606ade08653dd8a43334f0a7fb45504c5cc upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/iommu/intel-iommu.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -778,7 +778,11 @@ static struct dma_pte *pfn_to_dma_pte(st
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) {