[PATCH v3 10/10] iommu/vt-d: Use bounce buffer for untrusted devices

Lu Baolu
2019-04-21T01:25:39Z

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 a whole IOMMU page.

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 | 138 ++++++++++++++++++++++++++----------
1 file changed, 99 insertions(+), 39 deletions(-)

diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index ed941ec9b9d5..52ccbd3f1425 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"
@@ -3410,15 +3411,17 @@ static int iommu_no_mapping(struct device *dev)
}

static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr,
- size_t size, int dir, u64 dma_mask)
+ size_t size, enum dma_data_direction dir,
+ unsigned long attrs, u64 dma_mask)
{
struct dmar_domain *domain;
- phys_addr_t start_paddr;
+ dma_addr_t start_dma;
unsigned long iova_pfn;
int prot = 0;
int ret;
struct intel_iommu *iommu;
unsigned long paddr_pfn = paddr >> PAGE_SHIFT;
+ unsigned long nrpages;

BUG_ON(dir == DMA_NONE);

@@ -3430,9 +3433,10 @@ static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr,
return DMA_MAPPING_ERROR;

iommu = domain_get_iommu(domain);
- size = aligned_nrpages(paddr, size);
+ nrpages = aligned_nrpages(paddr, size);

- iova_pfn = intel_alloc_iova(dev, domain, dma_to_mm_pfn(size), dma_mask);
+ iova_pfn = intel_alloc_iova(dev, domain,
+ dma_to_mm_pfn(nrpages), dma_mask);
if (!iova_pfn)
goto error;

@@ -3445,24 +3449,33 @@ static dma_addr_t __intel_map_single(struct device *dev, phys_addr_t paddr,
prot |= DMA_PTE_READ;
if (dir == DMA_FROM_DEVICE || dir == DMA_BIDIRECTIONAL)
prot |= DMA_PTE_WRITE;
+
+ start_dma = (dma_addr_t)iova_pfn << PAGE_SHIFT;
+ start_dma += offset_in_page(paddr);
+
/*
* paddr - (paddr + size) might be partial page, we should map the whole
* page. Note: if two part of one page are separately mapped, we
* might have two guest_addr mapping to the same host paddr, but this
* is not a big problem
*/
- ret = domain_pfn_mapping(domain, mm_to_dma_pfn(iova_pfn),
- mm_to_dma_pfn(paddr_pfn), size, prot);
+ if (device_needs_bounce(dev)) {
+ ret = iommu_bounce_map(dev, start_dma, paddr, size, dir, attrs);
+ if (!ret)
+ trace_bounce_map_single(dev, start_dma, paddr, size);
+ } else {
+ ret = domain_pfn_mapping(domain, mm_to_dma_pfn(iova_pfn),
+ mm_to_dma_pfn(paddr_pfn),
+ nrpages, prot);
+ }
if (ret)
goto error;

- start_paddr = (phys_addr_t)iova_pfn << PAGE_SHIFT;
- start_paddr += paddr & ~PAGE_MASK;
- return start_paddr;
-
+ return start_dma;
error:
if (iova_pfn)
- free_iova_fast(&domain->iovad, iova_pfn, dma_to_mm_pfn(size));
+ free_iova_fast(&domain->iovad, iova_pfn,
+ dma_to_mm_pfn(nrpages));
dev_err(dev, "Device request: %zx@%llx dir %d --- failed\n",
size, (unsigned long long)paddr, dir);
return DMA_MAPPING_ERROR;
@@ -3474,44 +3487,79 @@ static dma_addr_t intel_map_page(struct device *dev, struct page *page,
unsigned long attrs)
{
return __intel_map_single(dev, page_to_phys(page) + offset, size,
- dir, *dev->dma_mask);
+ dir, attrs, *dev->dma_mask);
}

static dma_addr_t intel_map_resource(struct device *dev, phys_addr_t phys_addr,
size_t size, enum dma_data_direction dir,
unsigned long attrs)
{
- return __intel_map_single(dev, phys_addr, size, dir, *dev->dma_mask);
+ return __intel_map_single(dev, phys_addr, size,
+ dir, attrs, *dev->dma_mask);
}

-static void intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size)
+static void
+intel_unmap(struct device *dev, dma_addr_t dev_addr, size_t size,
+ struct scatterlist *sglist, int nelems,
+ enum dma_data_direction dir, unsigned long attrs)
{
struct dmar_domain *domain;
unsigned long start_pfn, last_pfn;
- unsigned long nrpages;
+ unsigned long nrpages = 0;
unsigned long iova_pfn;
struct intel_iommu *iommu;
- struct page *freelist;
+ struct page *freelist = NULL;
+ struct pci_dev *pdev = NULL;

if (iommu_no_mapping(dev))
return;

+ if (dev_is_pci(dev))
+ pdev = to_pci_dev(dev);
+
domain = find_domain(dev);
BUG_ON(!domain);

iommu = domain_get_iommu(domain);

- 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;
-
- dev_dbg(dev, "Device unmapping: pfn %lx-%lx\n", start_pfn, last_pfn);
+ if (sglist) {
+ struct scatterlist *sg;
+ int i;

- freelist = domain_unmap(domain, start_pfn, last_pfn);
+ dev_addr = sg_dma_address(sglist) & PAGE_MASK;
+ iova_pfn = IOVA_PFN(dev_addr);
+ for_each_sg(sglist, sg, nelems, i) {
+ nrpages += aligned_nrpages(sg_dma_address(sg),
+ sg_dma_len(sg));
+ }
+ start_pfn = mm_to_dma_pfn(iova_pfn);
+ last_pfn = start_pfn + nrpages - 1;
+
+ 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;
+
+ 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 (intel_iommu_strict) {
+ if (intel_iommu_strict || (pdev && pdev->untrusted)) {
iommu_flush_iotlb_psi(iommu, domain, start_pfn,
nrpages, !freelist, 0);
/* free iova */
@@ -3531,7 +3579,7 @@ static void intel_unmap_page(struct device *dev, dma_addr_t dev_addr,
size_t size, enum dma_data_direction dir,
unsigned long attrs)
{
- intel_unmap(dev, dev_addr, size);
+ intel_unmap(dev, dev_addr, size, NULL, 0, dir, attrs);
}

static void *intel_alloc_coherent(struct device *dev, size_t size,
@@ -3572,7 +3620,7 @@ static void *intel_alloc_coherent(struct device *dev, size_t size,
memset(page_address(page), 0, size);

*dma_handle = __intel_map_single(dev, page_to_phys(page), size,
- DMA_BIDIRECTIONAL,
+ DMA_BIDIRECTIONAL, attrs,
dev->coherent_dma_mask);
if (*dma_handle != DMA_MAPPING_ERROR)
return page_address(page);
@@ -3591,7 +3639,7 @@ static void intel_free_coherent(struct device *dev, size_t size, void *vaddr,
size = PAGE_ALIGN(size);
order = get_order(size);

- intel_unmap(dev, dma_handle, size);
+ intel_unmap(dev, dma_handle, size, NULL, 0, 0, attrs);
if (!dma_release_from_contiguous(dev, page, size >> PAGE_SHIFT))
__free_pages(page, order);
}
@@ -3600,16 +3648,7 @@ static void intel_unmap_sg(struct device *dev, struct scatterlist *sglist,
int nelems, enum dma_data_direction dir,
unsigned long attrs)
{
- dma_addr_t startaddr = sg_dma_address(sglist) & PAGE_MASK;
- unsigned long nrpages = 0;
- struct scatterlist *sg;
- int i;
-
- for_each_sg(sglist, sg, nelems, i) {
- nrpages += aligned_nrpages(sg_dma_address(sg), sg_dma_len(sg));
- }
-
- intel_unmap(dev, startaddr, nrpages << VTD_PAGE_SHIFT);
+ intel_unmap(dev, 0, 0, sglist, nelems, dir, attrs);
}

static int intel_nontranslate_map_sg(struct device *hddev,
@@ -3671,7 +3710,28 @@ static int intel_map_sg(struct device *dev, struct scatterlist *sglist, int nele

start_vpfn = mm_to_dma_pfn(iova_pfn);

- ret = domain_sg_mapping(domain, start_vpfn, sglist, size, prot);
+ if (device_needs_bounce(dev)) {
+ for_each_sg(sglist, sg, nelems, i) {
+ unsigned int pgoff = offset_in_page(sg->offset);
+ dma_addr_t addr;
+
+ addr = ((dma_addr_t)iova_pfn << PAGE_SHIFT) + pgoff;
+ ret = iommu_bounce_map(dev, addr, sg_phys(sg),
+ sg->length, dir, attrs);
+ if (ret)
+ break;
+
+ trace_bounce_map_sg(dev, i, nelems, addr,
+ sg_phys(sg), sg->length);
+
+ sg->dma_address = addr;
+ sg->dma_length = sg->length;
+ iova_pfn += aligned_nrpages(sg->offset, sg->length);
+ }
+ } else {
+ ret = domain_sg_mapping(domain, start_vpfn, sglist, size, prot);
+ }
+
if (unlikely(ret)) {
dma_pte_free_pagetable(domain, start_vpfn,
start_vpfn + size - 1,
--
2.17.1