The lazy IOTLB flushing setup leaves a time window, in which the device can still access some system memory, which has already been unmapped by the device driver. It's not suitable for untrusted devices. A malicious device might use this to attack the system by obtaining data that it shouldn't obtain.
Fixes: c588072bba6b5 ("iommu/vt-d: Convert intel iommu driver to the iommu ops") Signed-off-by: Lu Baolu <baolu...@linux.intel.com> --- drivers/iommu/dma-iommu.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c index f659395e7959..65234e383d6b 100644 --- a/drivers/iommu/dma-iommu.c +++ b/drivers/iommu/dma-iommu.c @@ -311,6 +311,11 @@ static void iommu_dma_flush_iotlb_all(struct iova_domain *iovad) domain->ops->flush_iotlb_all(domain); } +static bool dev_is_untrusted(struct device *dev) +{ + return dev_is_pci(dev) && to_pci_dev(dev)->untrusted; +} + /** * iommu_dma_init_domain - Initialise a DMA mapping domain * @domain: IOMMU domain previously prepared by iommu_get_dma_cookie() @@ -365,8 +370,9 @@ static int iommu_dma_init_domain(struct iommu_domain *domain, dma_addr_t base, init_iova_domain(iovad, 1UL << order, base_pfn); - if (!cookie->fq_domain && !iommu_domain_get_attr(domain, - DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE, &attr) && attr) { + if (!cookie->fq_domain && (!dev || !dev_is_untrusted(dev)) && + !iommu_domain_get_attr(domain, DOMAIN_ATTR_DMA_USE_FLUSH_QUEUE, &attr) && + attr) { if (init_iova_flush_queue(iovad, iommu_dma_flush_iotlb_all, iommu_dma_entry_dtor)) pr_warn("iova flush queue initialization failed\n"); @@ -508,11 +514,6 @@ static void __iommu_dma_unmap_swiotlb(struct device *dev, dma_addr_t dma_addr, iova_align(iovad, size), dir, attrs); } -static bool dev_is_untrusted(struct device *dev) -{ - return dev_is_pci(dev) && to_pci_dev(dev)->untrusted; -} - static dma_addr_t __iommu_dma_map(struct device *dev, phys_addr_t phys, size_t size, int prot, u64 dma_mask) { -- 2.25.1