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Subject[PATCH v8 7/7] iommu/vt-d: Use bounce buffer for untrusted devices
Date
The Intel VT-d hardware uses paging for DMA remapping.
The minimum mapped window is a page size. The device
drivers may map buffers not filling the whole IOMMU
window. This allows the device to access to possibly
unrelated memory and a malicious device could exploit
this to perform DMA attacks. To address this, the
Intel IOMMU driver will use bounce pages for those
buffers which don't fill whole IOMMU pages.

Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
Cc: Kevin Tian <kevin.tian@intel.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Tested-by: Xu Pengfei <pengfei.xu@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@intel.com>
---
drivers/iommu/intel-iommu.c | 244 ++++++++++++++++++++++++++++++++++++
1 file changed, 244 insertions(+)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index eb2a13e39eca..2800c52eee89 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -41,9 +41,11 @@
#include <linux/dma-direct.h>
#include <linux/crash_dump.h>
#include <linux/numa.h>
+#include <linux/swiotlb.h>
#include <asm/irq_remapping.h>
#include <asm/cacheflush.h>
#include <asm/iommu.h>
+#include <trace/events/intel_iommu.h>

#include "irq_remapping.h"
#include "intel-pasid.h"
@@ -346,6 +348,8 @@ static int domain_detach_iommu(struct dmar_domain *domain,
static bool device_is_rmrr_locked(struct device *dev);
static int intel_iommu_attach_device(struct iommu_domain *domain,
struct device *dev);
+static phys_addr_t intel_iommu_iova_to_phys(struct iommu_domain *domain,
+ dma_addr_t iova);

#ifdef CONFIG_INTEL_IOMMU_DEFAULT_ON
int dmar_disabled = 0;
@@ -3775,6 +3779,238 @@ static const struct dma_map_ops intel_dma_ops = {
.dma_supported = dma_direct_supported,
};

+static void
+bounce_sync_single(struct device *dev, dma_addr_t addr, size_t size,
+ enum dma_data_direction dir, enum dma_sync_target target)
+{
+ struct dmar_domain *domain;
+ phys_addr_t tlb_addr;
+
+ domain = find_domain(dev);
+ if (WARN_ON(!domain))
+ return;
+
+ tlb_addr = intel_iommu_iova_to_phys(&domain->domain, addr);
+ if (is_swiotlb_buffer(tlb_addr))
+ swiotlb_tbl_sync_single(dev, tlb_addr, size, dir, target);
+}
+
+static dma_addr_t
+bounce_map_single(struct device *dev, phys_addr_t paddr, size_t size,
+ enum dma_data_direction dir, unsigned long attrs,
+ u64 dma_mask)
+{
+ size_t aligned_size = ALIGN(size, VTD_PAGE_SIZE);
+ struct dmar_domain *domain;
+ struct intel_iommu *iommu;
+ unsigned long iova_pfn;
+ unsigned long nrpages;
+ phys_addr_t tlb_addr;
+ int prot = 0;
+ int ret;
+
+ domain = find_domain(dev);
+ if (WARN_ON(dir == DMA_NONE || !domain))
+ return DMA_MAPPING_ERROR;
+
+ iommu = domain_get_iommu(domain);
+ if (WARN_ON(!iommu))
+ return DMA_MAPPING_ERROR;
+
+ nrpages = aligned_nrpages(0, size);
+ iova_pfn = intel_alloc_iova(dev, domain,
+ dma_to_mm_pfn(nrpages), dma_mask);
+ if (!iova_pfn)
+ return DMA_MAPPING_ERROR;
+
+ /*
+ * Check if DMAR supports zero-length reads on write only
+ * mappings..
+ */
+ if (dir == DMA_TO_DEVICE || dir == DMA_BIDIRECTIONAL ||
+ !cap_zlr(iommu->cap))
+ prot |= DMA_PTE_READ;
+ if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
+ prot |= DMA_PTE_WRITE;
+
+ /*
+ * If both the physical buffer start address and size are
+ * page aligned, we don't need to use a bounce page.
+ */
+ if (!IS_ALIGNED(paddr | size, VTD_PAGE_SIZE)) {
+ tlb_addr = swiotlb_tbl_map_single(dev,
+ __phys_to_dma(dev, io_tlb_start),
+ paddr, size, aligned_size, dir, attrs);
+ if (tlb_addr == DMA_MAPPING_ERROR)
+ goto swiotlb_error;
+ } else {
+ tlb_addr = paddr;
+ }
+
+ ret = domain_pfn_mapping(domain, mm_to_dma_pfn(iova_pfn),
+ tlb_addr >> VTD_PAGE_SHIFT, nrpages, prot);
+ if (ret)
+ goto mapping_error;
+
+ trace_bounce_map_single(dev, iova_pfn << PAGE_SHIFT, paddr, size);
+
+ return (phys_addr_t)iova_pfn << PAGE_SHIFT;
+
+mapping_error:
+ if (is_swiotlb_buffer(tlb_addr))
+ swiotlb_tbl_unmap_single(dev, tlb_addr, size,
+ aligned_size, dir, attrs);
+swiotlb_error:
+ free_iova_fast(&domain->iovad, iova_pfn, dma_to_mm_pfn(nrpages));
+ dev_err(dev, "Device bounce map: %zx@%llx dir %d --- failed\n",
+ size, (unsigned long long)paddr, dir);
+
+ return DMA_MAPPING_ERROR;
+}
+
+static void
+bounce_unmap_single(struct device *dev, dma_addr_t dev_addr, size_t size,
+ enum dma_data_direction dir, unsigned long attrs)
+{
+ size_t aligned_size = ALIGN(size, VTD_PAGE_SIZE);
+ struct dmar_domain *domain;
+ phys_addr_t tlb_addr;
+
+ domain = find_domain(dev);
+ if (WARN_ON(!domain))
+ return;
+
+ tlb_addr = intel_iommu_iova_to_phys(&domain->domain, dev_addr);
+ if (WARN_ON(!tlb_addr))
+ return;
+
+ intel_unmap(dev, dev_addr, size);
+ if (is_swiotlb_buffer(tlb_addr))
+ swiotlb_tbl_unmap_single(dev, tlb_addr, size,
+ aligned_size, dir, attrs);
+
+ trace_bounce_unmap_single(dev, dev_addr, size);
+}
+
+static dma_addr_t
+bounce_map_page(struct device *dev, struct page *page, unsigned long offset,
+ size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+ return bounce_map_single(dev, page_to_phys(page) + offset,
+ size, dir, attrs, *dev->dma_mask);
+}
+
+static dma_addr_t
+bounce_map_resource(struct device *dev, phys_addr_t phys_addr, size_t size,
+ enum dma_data_direction dir, unsigned long attrs)
+{
+ return bounce_map_single(dev, phys_addr, size,
+ dir, attrs, *dev->dma_mask);
+}
+
+static void
+bounce_unmap_page(struct device *dev, dma_addr_t dev_addr, size_t size,
+ enum dma_data_direction dir, unsigned long attrs)
+{
+ bounce_unmap_single(dev, dev_addr, size, dir, attrs);
+}
+
+static void
+bounce_unmap_resource(struct device *dev, dma_addr_t dev_addr, size_t size,
+ enum dma_data_direction dir, unsigned long attrs)
+{
+ bounce_unmap_single(dev, dev_addr, size, dir, attrs);
+}
+
+static void
+bounce_unmap_sg(struct device *dev, struct scatterlist *sglist, int nelems,
+ enum dma_data_direction dir, unsigned long attrs)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sglist, sg, nelems, i)
+ bounce_unmap_page(dev, sg->dma_address,
+ sg_dma_len(sg), dir, attrs);
+}
+
+static int
+bounce_map_sg(struct device *dev, struct scatterlist *sglist, int nelems,
+ enum dma_data_direction dir, unsigned long attrs)
+{
+ int i;
+ struct scatterlist *sg;
+
+ for_each_sg(sglist, sg, nelems, i) {
+ sg->dma_address = bounce_map_page(dev, sg_page(sg),
+ sg->offset, sg->length,
+ dir, attrs);
+ if (sg->dma_address == DMA_MAPPING_ERROR)
+ goto out_unmap;
+ sg_dma_len(sg) = sg->length;
+ }
+
+ return nelems;
+
+out_unmap:
+ bounce_unmap_sg(dev, sglist, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+ return 0;
+}
+
+static void
+bounce_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
+ size_t size, enum dma_data_direction dir)
+{
+ bounce_sync_single(dev, addr, size, dir, SYNC_FOR_CPU);
+}
+
+static void
+bounce_sync_single_for_device(struct device *dev, dma_addr_t addr,
+ size_t size, enum dma_data_direction dir)
+{
+ bounce_sync_single(dev, addr, size, dir, SYNC_FOR_DEVICE);
+}
+
+static void
+bounce_sync_sg_for_cpu(struct device *dev, struct scatterlist *sglist,
+ int nelems, enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sglist, sg, nelems, i)
+ bounce_sync_single(dev, sg_dma_address(sg),
+ sg_dma_len(sg), dir, SYNC_FOR_CPU);
+}
+
+static void
+bounce_sync_sg_for_device(struct device *dev, struct scatterlist *sglist,
+ int nelems, enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ for_each_sg(sglist, sg, nelems, i)
+ bounce_sync_single(dev, sg_dma_address(sg),
+ sg_dma_len(sg), dir, SYNC_FOR_DEVICE);
+}
+
+static const struct dma_map_ops bounce_dma_ops = {
+ .alloc = intel_alloc_coherent,
+ .free = intel_free_coherent,
+ .map_sg = bounce_map_sg,
+ .unmap_sg = bounce_unmap_sg,
+ .map_page = bounce_map_page,
+ .unmap_page = bounce_unmap_page,
+ .sync_single_for_cpu = bounce_sync_single_for_cpu,
+ .sync_single_for_device = bounce_sync_single_for_device,
+ .sync_sg_for_cpu = bounce_sync_sg_for_cpu,
+ .sync_sg_for_device = bounce_sync_sg_for_device,
+ .map_resource = bounce_map_resource,
+ .unmap_resource = bounce_unmap_resource,
+ .dma_supported = dma_direct_supported,
+};
+
static inline int iommu_domain_cache_init(void)
{
int ret = 0;
@@ -5368,6 +5604,11 @@ static int intel_iommu_add_device(struct device *dev)
}
}

+ if (device_needs_bounce(dev)) {
+ dev_info(dev, "Use Intel IOMMU bounce page dma_ops\n");
+ set_dma_ops(dev, &bounce_dma_ops);
+ }
+
return 0;
}

@@ -5385,6 +5626,9 @@ static void intel_iommu_remove_device(struct device *dev)
iommu_group_remove_device(dev);

iommu_device_unlink(&iommu->iommu, dev);
+
+ if (device_needs_bounce(dev))
+ set_dma_ops(dev, NULL);
}

static void intel_iommu_get_resv_regions(struct device *device,
--
2.17.1
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