linux-kernel - Re: [PATCH] cma: use unsigned type for count argument

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Message-ID: <alpine.DEB.2.00.1212261755450.4150@chino.kir.corp.google.com>
Date:	Wed, 26 Dec 2012 17:59:18 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Michal Nazarewicz <mpn@...gle.com>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] cma: use unsigned type for count argument

On Sat, 22 Dec 2012, Michal Nazarewicz wrote:

> So I think just adding the following, should be sufficient to make
> everyone happy:
> 
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index e34e3e0..e91743b 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -320,7 +320,7 @@ struct page *dma_alloc_from_contiguous(struct device *dev, unsigned int count,
>  	pr_debug("%s(cma %p, count %u, align %u)\n", __func__, (void *)cma,
>  		 count, align);
>  
> -	if (!count)
> +	if (!count || count > INT_MAX)
>  		return NULL;
>  
>  	mask = (1 << align) - 1;

How is this different than leaving the formal to have a signed type, i.e. 
drop your patch, and testing for count <= 0 instead?
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