[PATCH v8 7/7] dma-iommu: account for min_align_mask w/swiotlb

From: David Stevens <stevensd@chromium.org>
To: Robin Murphy <robin.murphy@arm.com>, Christoph Hellwig <hch@lst.de>
Cc: Joerg Roedel <joro@8bytes.org>, Will Deacon <will@kernel.org>,
	Lu Baolu <baolu.lu@linux.intel.com>, Tom Murphy <murphyt7@tcd.ie>,
	Rajat Jain <rajatja@google.com>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	David Stevens <stevensd@chromium.org>
Subject: [PATCH v8 7/7] dma-iommu: account for min_align_mask w/swiotlb
Date: Wed, 29 Sep 2021 11:33:00 +0900	[thread overview]
Message-ID: <20210929023300.335969-8-stevensd@google.com> (raw)
In-Reply-To: <20210929023300.335969-1-stevensd@google.com>

From: David Stevens <stevensd@chromium.org>

Pass the non-aligned size to __iommu_dma_map when using swiotlb bounce
buffers in iommu_dma_map_page, to account for min_align_mask.

To deal with granule alignment, __iommu_dma_map maps iova_align(size +
iova_off) bytes starting at phys - iova_off. If iommu_dma_map_page
passes aligned size when using swiotlb, then this becomes
iova_align(iova_align(orig_size) + iova_off). Normally iova_off will be
zero when using swiotlb. However, this is not the case for devices that
set min_align_mask. When iova_off is non-zero, __iommu_dma_map ends up
mapping an extra page at the end of the buffer. Beyond just being a
security issue, the extra page is not cleaned up by __iommu_dma_unmap.
This causes problems when the IOVA is reused, due to collisions in the
iommu driver.  Just passing the original size is sufficient, since
__iommu_dma_map will take care of granule alignment.

Fixes: 1f221a0d0dbf ("swiotlb: respect min_align_mask")
Signed-off-by: David Stevens <stevensd@chromium.org>
---
 drivers/iommu/dma-iommu.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 289c49ead01a..342359727a59 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -806,7 +806,6 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
 	struct iommu_domain *domain = iommu_get_dma_domain(dev);
 	struct iommu_dma_cookie *cookie = domain->iova_cookie;
 	struct iova_domain *iovad = &cookie->iovad;
-	size_t aligned_size = size;
 	dma_addr_t iova, dma_mask = dma_get_mask(dev);
 
 	/*
@@ -815,7 +814,7 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
 	 */
 	if (dev_use_swiotlb(dev) && iova_offset(iovad, phys | size)) {
 		void *padding_start;
-		size_t padding_size;
+		size_t padding_size, aligned_size;
 
 		aligned_size = iova_align(iovad, size);
 		phys = swiotlb_tbl_map_single(dev, phys, size, aligned_size,
@@ -840,7 +839,7 @@ static dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
 	if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
 		arch_sync_dma_for_device(phys, size, dir);
 
-	iova = __iommu_dma_map(dev, phys, aligned_size, prot, dma_mask);
+	iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
 	if (iova == DMA_MAPPING_ERROR && is_swiotlb_buffer(dev, phys))
 		swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
 	return iova;
-- 
2.33.0.685.g46640cef36-goog

