linux-kernel - [PATCH 1/2] dma-mapping check pfn validity in dma_common_{mmap,get

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Date:   Tue,  9 Jul 2019 07:20:10 -0700
From:   Christoph Hellwig <hch@....de>
To:     Russell King - ARM Linux admin <linux@...linux.org.uk>
Cc:     Roger Quadros <rogerq@...com>,
        Vignesh Raghavendra <vigneshr@...com>,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: [PATCH 1/2] dma-mapping check pfn validity in dma_common_{mmap,get_sgtable}

Check that the pfn returned from arch_dma_coherent_to_pfn refers to
a valid page and reject the mmap / get_sgtable requests otherwise.

Based on the arm implementation of the mmap and get_sgtable methods.

Signed-off-by: Christoph Hellwig <hch@....de>
---
 kernel/dma/mapping.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/kernel/dma/mapping.c b/kernel/dma/mapping.c
index 1f628e7ac709..b945239621d8 100644
--- a/kernel/dma/mapping.c
+++ b/kernel/dma/mapping.c
@@ -116,11 +116,16 @@ int dma_common_get_sgtable(struct device *dev, struct sg_table *sgt,
 	int ret;
 
 	if (!dev_is_dma_coherent(dev)) {
+		unsigned long pfn;
+
 		if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_COHERENT_TO_PFN))
 			return -ENXIO;
 
-		page = pfn_to_page(arch_dma_coherent_to_pfn(dev, cpu_addr,
-				dma_addr));
+		/* If the PFN is not valid, we do not have a struct page */
+		pfn = arch_dma_coherent_to_pfn(dev, cpu_addr, dma_addr);
+		if (!pfn_valid(pfn))
+			return -ENXIO;
+		page = pfn_to_page(pfn);
 	} else {
 		page = virt_to_page(cpu_addr);
 	}
@@ -170,7 +175,11 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
 	if (!dev_is_dma_coherent(dev)) {
 		if (!IS_ENABLED(CONFIG_ARCH_HAS_DMA_COHERENT_TO_PFN))
 			return -ENXIO;
+
+		/* If the PFN is not valid, we do not have a struct page */
 		pfn = arch_dma_coherent_to_pfn(dev, cpu_addr, dma_addr);
+		if (!pfn_valid(pfn))
+			return -ENXIO;
 	} else {
 		pfn = page_to_pfn(virt_to_page(cpu_addr));
 	}
-- 
2.20.1