[PATCH v8 7/7] iommu/vt-d: Use bounce buffer for untrusted devices

[Lu Baolu]

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@xxxxxxxxx>
Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Tested-by: Xu Pengfei <pengfei.xu@xxxxxxxxx>
Tested-by: Mika Westerberg <mika.westerberg@xxxxxxxxx>
---
 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