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From: Julian Stecklina <jsteckli@os.info.tu-dresden.de>
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Subject: [PATCH] vfio, iommu: Fixed interaction of VFIO_IOMMU_MAP_DMA with IOMMU address limits
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The BUG_ON in drivers/iommu/intel-iommu.c:785 can be triggered from userspace via
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VFIO by calling the VFIO_IOMMU_MAP_DMA ioctl on a vfio device with any address
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beyond the addressing capabilities of the IOMMU. The problem is that the ioctl code
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calls iommu_iova_to_phys before it calls iommu_map. iommu_map handles the case that
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it gets addresses beyond the addressing capabilities of its IOMMU.
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intel_iommu_iova_to_phys does not.
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This patch fixes iommu_iova_to_phys to return NULL for addresses beyond what the
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IOMMU can handle. This in turn causes the ioctl call to fail in iommu_map and
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(correctly) return EFAULT to the user with a helpful warning message in the kernel
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log.
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Signed-off-by: Julian Stecklina <jsteckli@os.inf.tu-dresden.de>
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---
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drivers/iommu/intel-iommu.c | 6 +++++-
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1 file changed, 5 insertions(+), 1 deletion(-)
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diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
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index eec0d3e..61303db 100644
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--- a/drivers/iommu/intel-iommu.c
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+++ b/drivers/iommu/intel-iommu.c
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@@ -782,7 +782,11 @@ static struct dma_pte *pfn_to_dma_pte(struct dmar_domain *domain,
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int offset;
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BUG_ON(!domain->pgd);
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- BUG_ON(addr_width < BITS_PER_LONG && pfn >> addr_width);
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+
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+ if (addr_width < BITS_PER_LONG && pfn >> addr_width)
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+ /* Address beyond IOMMU's addressing capabilities. */
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+ return NULL;
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+
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parent = domain->pgd;
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while (level > 0) {
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--
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1.8.3.1
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