linux-kernel - Re: [PATCH v2] ARM/dma-mapping: use kvzalloc() in __iommu_alloc

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Message-ID: <5c84eec0-c249-6e8f-590b-cbb32bad3601@arm.com>
Date:   Thu, 27 Aug 2020 19:27:00 +0100
From:   Robin Murphy <robin.murphy@....com>
To:     Denis Efremov <efremov@...ux.com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Russell King <linux@...linux.org.uk>
Subject: Re: [PATCH v2] ARM/dma-mapping: use kvzalloc() in
 __iommu_alloc_buffer()

On 2020-08-27 16:43, Denis Efremov wrote:
> Use kvzalloc() in __iommu_alloc_buffer() instead of open-coding it.
> Size computation wrapped in array_size() macro to prevent potential
> integer overflows.

FWIW I'm currently working on a much more thorough cleanup by way of 
removing this code entirely [1] ;)

Robin.

[1] 
https://lore.kernel.org/linux-arm-kernel/cover.1597931875.git.robin.murphy@arm.com/

> Signed-off-by: Denis Efremov <efremov@...ux.com>
> ---
> Changes in v2:
>   - array_size() added
> 
>   arch/arm/mm/dma-mapping.c | 6 +-----
>   1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index 8a8949174b1c..c1f864ff7b84 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1199,14 +1199,10 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
>   {
>   	struct page **pages;
>   	int count = size >> PAGE_SHIFT;
> -	int array_size = count * sizeof(struct page *);
>   	int i = 0;
>   	int order_idx = 0;
>   
> -	if (array_size <= PAGE_SIZE)
> -		pages = kzalloc(array_size, GFP_KERNEL);
> -	else
> -		pages = vzalloc(array_size);
> +	pages = kvzalloc(array_size(sizeof(*pages), count), GFP_KERNEL);
>   	if (!pages)
>   		return NULL;
>   
>