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

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Message-ID: <826077f1-dc96-49be-961b-e9cfbed1fef5@gmail.com>
Date: Mon, 12 Feb 2024 16:50:12 +0100
From: Matthias Brugger <matthias.bgg@...il.com>
To: Erick Archer <erick.archer@....com>, Yong Wu <yong.wu@...iatek.com>,
 Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
 Robin Murphy <robin.murphy@....com>,
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 "Gustavo A. R. Silva" <gustavoars@...nel.org>,
 Kees Cook <keescook@...omium.org>
Cc: 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: Re: [PATCH] iommu/mtk_iommu: Use devm_kcalloc() instead of
 devm_kzalloc()



On 11/02/2024 19:22, Erick Archer wrote:
> 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>

Reviewed-by: Matthias Brugger <matthias.bgg@...il.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
>