[PATCH v4 6/6] arm: dma-mapping: updates to limit dma_mask and iommu mapping size

[Murali Karicheri <m-karicheri2@ti.com>]

Limit the dma_mask to minimum of dma_mask and dma_base + size - 1.

Also arm_iommu_create_mapping() has size parameter of size_t and
arm_setup_iommu_dma_ops() can take a value higher than that. So
limit the size to SIZE_MAX.

Signed-off-by: Murali Karicheri <m-karicheri2@ti.com>
---
 arch/arm/mm/dma-mapping.c |   10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
index 7864797..a1f9030 100644
--- a/arch/arm/mm/dma-mapping.c
+++ b/arch/arm/mm/dma-mapping.c
@@ -2004,6 +2004,13 @@ static bool arm_setup_iommu_dma_ops(struct device *dev, u64 dma_base, u64 size,
 	if (!iommu)
 		return false;
 
+	/*
+	 * currently arm_iommu_create_mapping() takes a max of size_t
+	 * for size param. So check this limit for now.
+	 */
+	if (size > SIZE_MAX)
+		return false;
+
 	mapping = arm_iommu_create_mapping(dev->bus, dma_base, size);
 	if (IS_ERR(mapping)) {
 		pr_warn("Failed to create %llu-byte IOMMU mapping for device %s\n",
@@ -2053,6 +2060,9 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size,
 {
 	struct dma_map_ops *dma_ops;
 
+	/* limit dma_mask to the lower of the two values */
+	*dev->dma_mask = min((*dev->dma_mask), (dma_base + size - 1));
+
 	dev->archdata.dma_coherent = coherent;
 	if (arm_setup_iommu_dma_ops(dev, dma_base, size, iommu))
 		dma_ops = arm_get_iommu_dma_map_ops(coherent);
-- 
1.7.9.5