linux-kernel - Re: [PATCH 2/2] Fix variable "error" missing initialization

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Message-ID: <20150429172457.GD2588@mguzik>
Date:	Wed, 29 Apr 2015 19:24:58 +0200
From:	Mateusz Guzik <mguzik@...hat.com>
To:	Shawn Chang <citypw@...il.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: [PATCH 2/2] Fix variable "error" missing initialization

On Thu, Apr 30, 2015 at 12:00:34AM +0800, Shawn Chang wrote:
> From: Shawn C <citypw@...il.com>
> 
> Signed-off-by: Shawn C <citypw@...il.com>
> ---
>  mm/mlock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/mlock.c b/mm/mlock.c
> index c7f6785..660e5c5 100644
> --- a/mm/mlock.c
> +++ b/mm/mlock.c
> @@ -557,7 +557,7 @@ static int do_mlock(unsigned long start, size_t len, int on)
>  {
>  	unsigned long nstart, end, tmp;
>  	struct vm_area_struct * vma, * prev;
> -	int error;
> +	int error = 0;
>  
>  	VM_BUG_ON(start & ~PAGE_MASK);
>  	VM_BUG_ON(len != PAGE_ALIGN(len));
> -- 
> 1.9.1
> 

This change does not make sense.

The very first read of error is after it gets set.

I see you sent another patch which credited grsecurity. In their
patchset it makes sense - do_mlock is modified in a way which can
interrupt the loop upcoming loop before it gets the chance to set error.

-- 
Mateusz Guzik
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