linux-hardening - [PATCH] iommu/mtk_iommu: Use devm_kcalloc() instead of devm

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Date: Sun, 11 Feb 2024 19:22:50 +0100
From: Erick Archer <erick.archer@....com>
To: Yong Wu <yong.wu@...iatek.com>,
	Joerg Roedel <joro@...tes.org>,
	Will Deacon <will@...nel.org>,
	Robin Murphy <robin.murphy@....com>,
	Matthias Brugger <matthias.bgg@...il.com>,
	AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
	"Gustavo A. R. Silva" <gustavoars@...nel.org>,
	Kees Cook <keescook@...omium.org>
Cc: Erick Archer <erick.archer@....com>,
	iommu@...ts.linux.dev,
	linux-mediatek@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-hardening@...r.kernel.org
Subject: [PATCH] iommu/mtk_iommu: Use devm_kcalloc() instead of devm_kzalloc()

This is an effort to get rid of all multiplications from allocation
functions in order to prevent integer overflows [1].

Here the multiplication is obviously safe because MTK_PROTECT_PA_ALIGN
is defined as a literal value of 256 or 128.

For the "mtk_iommu.c" file: 256
For the "mtk_iommu_v1.c" file: 128

However, using devm_kcalloc() is more appropriate [2] and improves
readability. This patch has no effect on runtime behavior.

Link: https://github.com/KSPP/linux/issues/162 [1]
Link: https://www.kernel.org/doc/html/next/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments [2]
Signed-off-by: Erick Archer <erick.archer@....com>
---
 drivers/iommu/mtk_iommu.c    | 2 +-
 drivers/iommu/mtk_iommu_v1.c | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/mtk_iommu.c b/drivers/iommu/mtk_iommu.c
index 7abe9e85a570..9aae6eb604b1 100644
--- a/drivers/iommu/mtk_iommu.c
+++ b/drivers/iommu/mtk_iommu.c
@@ -1264,7 +1264,7 @@ static int mtk_iommu_probe(struct platform_device *pdev)
 	data->plat_data = of_device_get_match_data(dev);

 	/* Protect memory. HW will access here while translation fault.*/
-	protect = devm_kzalloc(dev, MTK_PROTECT_PA_ALIGN * 2, GFP_KERNEL);
+	protect = devm_kcalloc(dev, 2, MTK_PROTECT_PA_ALIGN, GFP_KERNEL);
 	if (!protect)
 		return -ENOMEM;
 	data->protect_base = ALIGN(virt_to_phys(protect), MTK_PROTECT_PA_ALIGN);
diff --git a/drivers/iommu/mtk_iommu_v1.c b/drivers/iommu/mtk_iommu_v1.c
index 25b41222abae..45cd845d153f 100644
--- a/drivers/iommu/mtk_iommu_v1.c
+++ b/drivers/iommu/mtk_iommu_v1.c
@@ -621,8 +621,8 @@ static int mtk_iommu_v1_probe(struct platform_device *pdev)
 	data->dev = dev;

 	/* Protect memory. HW will access here while translation fault.*/
-	protect = devm_kzalloc(dev, MTK_PROTECT_PA_ALIGN * 2,
-			GFP_KERNEL | GFP_DMA);
+	protect = devm_kcalloc(dev, 2, MTK_PROTECT_PA_ALIGN,
+			       GFP_KERNEL | GFP_DMA);
 	if (!protect)
 		return -ENOMEM;
 	data->protect_base = ALIGN(virt_to_phys(protect), MTK_PROTECT_PA_ALIGN);
--
2.25.1