[PATCH AUTOSEL 5.2 26/44] iommu/dma: Handle SG length overflow better

[PATCH AUTOSEL 5.2 26/44] iommu/dma: Handle SG length overflow better

[Sasha Levin]

From: Robin Murphy <robin.murphy@arm.com>

[ Upstream commit ab2cbeb0ed301a9f0460078e91b09f39958212ef ]

Since scatterlist dimensions are all unsigned ints, in the relatively
rare cases where a device's max_segment_size is set to UINT_MAX, then
the "cur_len + s_length <= max_len" check in __finalise_sg() will always
return true. As a result, the corner case of such a device mapping an
excessively large scatterlist which is mergeable to or beyond a total
length of 4GB can lead to overflow and a bogus truncated dma_length in
the resulting segment.

As we already assume that any single segment must be no longer than
max_len to begin with, this can easily be addressed by reshuffling the
comparison.

Fixes: 809eac54cdd6 ("iommu/dma: Implement scatterlist segment merging")
Reported-by: Nicolin Chen <nicoleotsuka@gmail.com>
Tested-by: Nicolin Chen <nicoleotsuka@gmail.com>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 drivers/iommu/dma-iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 379318266468c..8c02d2283d647 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -710,7 +710,7 @@ static int __finalise_sg(struct device *dev, struct scatterlist *sg, int nents,
 		 * - and wouldn't make the resulting output segment too long
 		 */
 		if (cur_len && !s_iova_off && (dma_addr & seg_mask) &&
-		    (cur_len + s_length <= max_len)) {
+		    (max_len - cur_len >= s_length)) {
 			/* ...then concatenate it with the previous one */
 			cur_len += s_length;
 		} else {
-- 
2.20.1

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[PATCH AUTOSEL 5.2 27/44] dma-direct: don't truncate dma_required_mask to bus addressing capabilities

[Sasha Levin]

From: Lucas Stach <l.stach@pengutronix.de>

[ Upstream commit d8ad55538abe443919e20e0bb996561bca9cad84 ]

The dma required_mask needs to reflect the actual addressing capabilities
needed to handle the whole system RAM. When truncated down to the bus
addressing capabilities dma_addressing_limited() will incorrectly signal
no limitations for devices which are restricted by the bus_dma_mask.

Fixes: b4ebe6063204 (dma-direct: implement complete bus_dma_mask handling)
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Tested-by: Atish Patra <atish.patra@wdc.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 kernel/dma/direct.c | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 2c2772e9702ab..9912be7a970de 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -55,9 +55,6 @@ u64 dma_direct_get_required_mask(struct device *dev)
 {
 	u64 max_dma = phys_to_dma_direct(dev, (max_pfn - 1) << PAGE_SHIFT);
 
-	if (dev->bus_dma_mask && dev->bus_dma_mask < max_dma)
-		max_dma = dev->bus_dma_mask;
-
 	return (1ULL << (fls64(max_dma) - 1)) * 2 - 1;
 }
 
-- 
2.20.1

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