linux-kernel - Re: [PATCH] ARM: DMA: Fix kzalloc flags in __iommu_alloc

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Message-id: <54897C14.3040702@samsung.com>
Date:	Thu, 11 Dec 2014 12:12:20 +0100
From:	Marek Szyprowski <m.szyprowski@...sung.com>
To:	Alexandre Courbot <acourbot@...dia.com>,
	Russell King <linux@....linux.org.uk>
Cc:	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	gnurou@...il.com, Arnd Bergmann <arnd@...db.de>,
	Thierry Reding <treding@...dia.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Subject: Re: [PATCH] ARM: DMA: Fix kzalloc flags in __iommu_alloc_buffer()


On 2014-12-08 09:39, Alexandre Courbot wrote:
> There doesn't seem to be any valid reason to allocate the pages array
> with the same flags as the buffer itself. Doing so can eventually lead
> to the following safeguard in mm/slab.c to be hit:
>
> BUG_ON(flags & GFP_SLAB_BUG_MASK);
>
> This happens when buffers are allocated with __GFP_DMA32 or
> __GFP_HIGHMEM.
>
> Fix this by allocating the pages array with GFP_KERNEL to follow what is
> done elsewhere in this file. Using GFP_KERNEL in __iommu_alloc_buffer()
> is safe because atomic allocations are handled by __iommu_alloc_atomic().
>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> Cc: Russell King <linux@....linux.org.uk>
> Cc: Marek Szyprowski <m.szyprowski@...sung.com>
> Cc: Arnd Bergmann <arnd@...db.de>
> Cc: Thierry Reding <treding@...dia.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>

Acked-by: Marek Szyprowski <m.szyprowski@...sung.com>

> ---
>   arch/arm/mm/dma-mapping.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/arm/mm/dma-mapping.c b/arch/arm/mm/dma-mapping.c
> index e8907117861e..bc495354c802 100644
> --- a/arch/arm/mm/dma-mapping.c
> +++ b/arch/arm/mm/dma-mapping.c
> @@ -1106,7 +1106,7 @@ static struct page **__iommu_alloc_buffer(struct device *dev, size_t size,
>   	int i = 0;
>   
>   	if (array_size <= PAGE_SIZE)
> -		pages = kzalloc(array_size, gfp);
> +		pages = kzalloc(array_size, GFP_KERNEL);
>   	else
>   		pages = vzalloc(array_size);
>   	if (!pages)

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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