linux-kernel - Re: [PATCH] mm/ksm: return NULL when doesn't get mergeable page

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Message-ID: <20130919083329.GA1620@thinkpad-work.brq.redhat.com>
Date:	Thu, 19 Sep 2013 10:33:29 +0200
From:	Petr Holasek <pholasek@...hat.com>
To:	Jianguo Wu <wujianguo@...wei.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Hugh Dickins <hughd@...gle.com>, Mel Gorman <mgorman@...e.de>,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/ksm: return NULL when doesn't get mergeable page

On Mon, 16 Sep 2013, Jianguo Wu wrote:
> In get_mergeable_page() local variable page is not initialized,
> it may hold a garbage value, when find_mergeable_vma() return NULL,
> get_mergeable_page() may return a garbage value to the caller.
> 
> So initialize page as NULL.
> 
> Signed-off-by: Jianguo Wu <wujianguo@...wei.com>
> ---
>  mm/ksm.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/mm/ksm.c b/mm/ksm.c
> index b6afe0c..87efbae 100644
> --- a/mm/ksm.c
> +++ b/mm/ksm.c
> @@ -460,7 +460,7 @@ static struct page *get_mergeable_page(struct rmap_item *rmap_item)
>  	struct mm_struct *mm = rmap_item->mm;
>  	unsigned long addr = rmap_item->address;
>  	struct vm_area_struct *vma;
> -	struct page *page;
> +	struct page *page = NULL;
>  
>  	down_read(&mm->mmap_sem);
>  	vma = find_mergeable_vma(mm, addr);
> -- 
> 1.7.1
> 

When find_mergeable_vma returned NULL, NULL is assigned to page in "out"
statement.
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