iommu: Don't use lazy flush for untrusted device

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.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20210225061454.2864009-1-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index f659395..65234e3 100644 (file)
--- 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)
 {