[PATCH v4 9/9] iommu/vt-d: Use bounce buffer for untrusted devices

Lu Baolu
2019-06-03T01:24:14Z

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 | 128 ++++++++++++++++++++++++++++++++----
1 file changed, 117 insertions(+), 11 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index 2f54734d1c43..4bf744a1c239 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -52,6 +52,7 @@
#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"
@@ -3537,6 +3538,19 @@ __intel_map_single(struct device *dev, phys_addr_t paddr, size_t size,
if (!iova_pfn)
goto error;

+ if (device_needs_bounce(dev)) {
+ dma_addr_t ret_addr;
+
+ ret_addr = iommu_bounce_map(dev, iova_pfn << PAGE_SHIFT,
+ paddr, size, dir, attrs);
+ if (ret_addr == DMA_MAPPING_ERROR)
+ goto error;
+ trace_bounce_map_single(dev, iova_pfn << PAGE_SHIFT,
+ paddr, size);
+
+ return ret_addr;
+ }
+
/*
* Check if DMAR supports zero-length reads on write only
* mappings..
@@ -3620,14 +3634,28 @@ static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size,
start_pfn = mm_to_dma_pfn(iova_pfn);
last_pfn = start_pfn + nrpages - 1;

- freelist = domain_unmap(domain, start_pfn, last_pfn);
+ if (device_needs_bounce(dev))
+ for_each_sg(sglist, sg, nelems, i) {
+ iommu_bounce_unmap(dev, sg_dma_address(sg),
+ sg->length, dir, attrs);
+ trace_bounce_unmap_sg(dev, i, nelems,
+ sg_dma_address(sg),
+ sg_phys(sg), sg->length);
+ }
+ else
+ freelist = domain_unmap(domain, start_pfn, last_pfn);
} else {
iova_pfn = IOVA_PFN(dev_addr);
nrpages = aligned_nrpages(dev_addr, size);
start_pfn = mm_to_dma_pfn(iova_pfn);
last_pfn = start_pfn + nrpages - 1;

- freelist = domain_unmap(domain, start_pfn, last_pfn);
+ if (device_needs_bounce(dev)) {
+ iommu_bounce_unmap(dev, dev_addr, size, dir, attrs);
+ trace_bounce_unmap_single(dev, dev_addr, size);
+ } else {
+ freelist = domain_unmap(domain, start_pfn, last_pfn);
+ }
}

if (dev_is_pci(dev))
@@ -3774,6 +3802,26 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele
prot |= DMA_PTE_WRITE;

start_vpfn = mm_to_dma_pfn(iova_pfn);
+ if (device_needs_bounce(dev)) {
+ for_each_sg(sglist, sg, nelems, i) {
+ dma_addr_t ret_addr;
+
+ ret_addr = iommu_bounce_map(dev,
+ start_vpfn << VTD_PAGE_SHIFT,
+ sg_phys(sg), sg->length, dir, attrs);
+ if (ret_addr == DMA_MAPPING_ERROR)
+ break;
+
+ trace_bounce_map_sg(dev, i, nelems, ret_addr,
+ sg_phys(sg), sg->length);
+
+ sg->dma_address = ret_addr;
+ sg->dma_length = sg->length;
+ start_vpfn += aligned_nrpages(sg->offset, sg->length);
+ }
+
+ return i;
+ }

ret = domain_sg_mapping(domain, start_vpfn, sglist, size, prot);
if (unlikely(ret)) {
@@ -3787,16 +3835,74 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele
return nelems;
}

+static void
+intel_sync_single_for_cpu(struct device *dev, dma_addr_t addr,
+ size_t size, enum dma_data_direction dir)
+{
+ if (!iommu_need_mapping(dev))
+ dma_direct_sync_single_for_cpu(dev, addr, size, dir);
+
+ if (device_needs_bounce(dev))
+ iommu_bounce_sync(dev, addr, size, dir, SYNC_FOR_CPU);
+}
+
+static void
+intel_sync_single_for_device(struct device *dev, dma_addr_t addr,
+ size_t size, enum dma_data_direction dir)
+{
+ if (!iommu_need_mapping(dev))
+ dma_direct_sync_single_for_device(dev, addr, size, dir);
+
+ if (device_needs_bounce(dev))
+ iommu_bounce_sync(dev, addr, size, dir, SYNC_FOR_DEVICE);
+}
+
+static void
+intel_sync_sg_for_cpu(struct device *dev, struct scatterlist *sglist,
+ int nelems, enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ if (!iommu_need_mapping(dev))
+ dma_direct_sync_sg_for_cpu(dev, sglist, nelems, dir);
+
+ if (device_needs_bounce(dev))
+ for_each_sg(sglist, sg, nelems, i)
+ iommu_bounce_sync(dev, sg_dma_address(sg),
+ sg_dma_len(sg), dir, SYNC_FOR_CPU);
+}
+
+static void
+intel_sync_sg_for_device(struct device *dev, struct scatterlist *sglist,
+ int nelems, enum dma_data_direction dir)
+{
+ struct scatterlist *sg;
+ int i;
+
+ if (!iommu_need_mapping(dev))
+ dma_direct_sync_sg_for_device(dev, sglist, nelems, dir);
+
+ if (device_needs_bounce(dev))
+ for_each_sg(sglist, sg, nelems, i)
+ iommu_bounce_sync(dev, sg_dma_address(sg),
+ sg_dma_len(sg), dir, SYNC_FOR_DEVICE);
+}
+
static const struct dma_map_ops intel_dma_ops = {
- .alloc = intel_alloc_coherent,
- .free = intel_free_coherent,
- .map_sg = intel_map_sg,
- .unmap_sg = intel_unmap_sg,
- .map_page = intel_map_page,
- .unmap_page = intel_unmap_page,
- .map_resource = intel_map_resource,
- .unmap_resource = intel_unmap_resource,
- .dma_supported = dma_direct_supported,
+ .alloc = intel_alloc_coherent,
+ .free = intel_free_coherent,
+ .map_sg = intel_map_sg,
+ .unmap_sg = intel_unmap_sg,
+ .map_page = intel_map_page,
+ .unmap_page = intel_unmap_page,
+ .sync_single_for_cpu = intel_sync_single_for_cpu,
+ .sync_single_for_device = intel_sync_single_for_device,
+ .sync_sg_for_cpu = intel_sync_sg_for_cpu,
+ .sync_sg_for_device = intel_sync_sg_for_device,
+ .map_resource = intel_map_resource,
+ .unmap_resource = intel_unmap_resource,
+ .dma_supported = dma_direct_supported,
};

static inline int iommu_domain_cache_init(void)
--
2.17.1