linux-kernel - Re: [PATCH] kexec: fix memory leak in function kimage_normal

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Message-Id: <20130222135938.c6f28ff5.akpm@linux-foundation.org>
Date:	Fri, 22 Feb 2013 13:59:38 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Zhang Yanfei <zhangyanfei@...fujitsu.com>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	"kexec@...ts.infradead.org" <kexec@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kexec: fix memory leak in function kimage_normal_alloc

On Fri, 22 Feb 2013 12:36:13 +0800
Zhang Yanfei <zhangyanfei@...fujitsu.com> wrote:

> If kimage_normal_alloc() fails to alloc pages for image->swap_page, it
> should call kimage_free_page_list() to free allocated pages in
> image->control_pages list before it frees image.
>
> ...
>
> --- a/kernel/kexec.c
> +++ b/kernel/kexec.c
> @@ -223,6 +223,8 @@ out:
>  
>  }
>  
> +static void kimage_free_page_list(struct list_head *list);
> +
>  static int kimage_normal_alloc(struct kimage **rimage, unsigned long entry,
>  				unsigned long nr_segments,
>  				struct kexec_segment __user *segments)
> @@ -248,22 +250,22 @@ static int kimage_normal_alloc(struct kimage **rimage, unsigned long entry,
>  					   get_order(KEXEC_CONTROL_PAGE_SIZE));
>  	if (!image->control_code_page) {
>  		printk(KERN_ERR "Could not allocate control_code_buffer\n");
> -		goto out;
> +		goto out_free;
>  	}
>  
>  	image->swap_page = kimage_alloc_control_pages(image, 0);
>  	if (!image->swap_page) {
>  		printk(KERN_ERR "Could not allocate swap buffer\n");
> -		goto out;
> +		goto out_free;
>  	}
>  
> -	result = 0;
> - out:
> -	if (result == 0)
> -		*rimage = image;
> -	else
> -		kfree(image);
> +	*rimage = image;
> +	return 0;
>  
> +out_free:
> +	kimage_free_page_list(&image->control_pages);
> +	kfree(image);
> +out:
>  	return result;
>  }

kimage_alloc_normal_control_pages() won't add any pages to the image if
one of its allocation attemtps failed.  So afaict the first `goto
out_free' could be just `goto out'.

The second `goto out_free' does appear to be needed: it frees the pages
allocated by the first call to kimage_alloc_control_pages().  I think. 
The kimage_alloc_control_pages() handling of image->type is a bit
twisty.

Please double-check the logic?
--
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