linux-kernel - Re: [PATCH v2 02/10] DMA, CMA: fix possible memory leak

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Message-ID: <20140612052543.GE12415@bbox>
Date:	Thu, 12 Jun 2014 14:25:43 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Aneesh Kumar K.V" <aneesh.kumar@...ux.vnet.ibm.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	kvm@...r.kernel.org, linux-mm@...ck.org,
	Gleb Natapov <gleb@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Alexander Graf <agraf@...e.de>, kvm-ppc@...r.kernel.org,
	linux-kernel@...r.kernel.org, Paul Mackerras <paulus@...ba.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paolo Bonzini <pbonzini@...hat.com>,
	linuxppc-dev@...ts.ozlabs.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 02/10] DMA, CMA: fix possible memory leak

On Thu, Jun 12, 2014 at 12:21:39PM +0900, Joonsoo Kim wrote:
> We should free memory for bitmap when we find zone mis-match,
> otherwise this memory will leak.

Then, -stable stuff?

> 
> Additionally, I copy code comment from ppc kvm's cma code to notify
> why we need to check zone mis-match.
> 
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> 
> diff --git a/drivers/base/dma-contiguous.c b/drivers/base/dma-contiguous.c
> index bd0bb81..fb0cdce 100644
> --- a/drivers/base/dma-contiguous.c
> +++ b/drivers/base/dma-contiguous.c
> @@ -177,14 +177,24 @@ static int __init cma_activate_area(struct cma *cma)
>  		base_pfn = pfn;
>  		for (j = pageblock_nr_pages; j; --j, pfn++) {
>  			WARN_ON_ONCE(!pfn_valid(pfn));
> +			/*
> +			 * alloc_contig_range requires the pfn range
> +			 * specified to be in the same zone. Make this
> +			 * simple by forcing the entire CMA resv range
> +			 * to be in the same zone.
> +			 */
>  			if (page_zone(pfn_to_page(pfn)) != zone)
> -				return -EINVAL;
> +				goto err;

At a first glance, I thought it would be better to handle such error
before activating.
So when I see the registration code(ie, dma_contiguous_revere_area),
I realized it is impossible because we didn't set up zone yet. :(

If so, when we detect to fail here, it would be better to report more
meaningful error message like what was successful zone and what is
new zone and failed pfn number?

>  		}
>  		init_cma_reserved_pageblock(pfn_to_page(base_pfn));
>  	} while (--i);
>  
>  	mutex_init(&cma->lock);
>  	return 0;
> +
> +err:
> +	kfree(cma->bitmap);
> +	return -EINVAL;
>  }
>  
>  static struct cma cma_areas[MAX_CMA_AREAS];
> -- 
> 1.7.9.5

-- 
Kind regards,
Minchan Kim
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