linux-kernel - Re: [PATCH 1/1] arch/parisc: mm: fix uninitialized variable usage

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Date:	Sun, 22 Sep 2013 18:58:09 -0400
From:	Johannes Weiner <hannes@...xchg.org>
To:	Felipe Pena <felipensp@...il.com>
Cc:	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	linux-parisc@...r.kernel.org, Michal Hocko <mhocko@...e.cz>,
	linux-kernel@...r.kernel.org,
	Kautuk Consul <consul.kautuk@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Helge Deller <deller@....de>
Subject: Re: [PATCH 1/1] arch/parisc: mm: fix uninitialized variable usage

Hello Felipe,

On Sun, Sep 22, 2013 at 03:17:46PM -0300, Felipe Pena wrote:
> The FAULT_FLAG_WRITE flag has been set based on uninitialized variable

Oops, you are right.

> Signed-off-by: Felipe Pena <felipensp@...il.com>
> ---
>  arch/parisc/mm/fault.c |    5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/parisc/mm/fault.c b/arch/parisc/mm/fault.c
> index d10d27a..6b38026 100644
> --- a/arch/parisc/mm/fault.c
> +++ b/arch/parisc/mm/fault.c
> @@ -182,8 +182,6 @@ void do_page_fault(struct pt_regs *regs, unsigned long code,
>  
>  	if (user_mode(regs))
>  		flags |= FAULT_FLAG_USER;
> -	if (acc_type & VM_WRITE)
> -		flags |= FAULT_FLAG_WRITE;
>  retry:
>  	down_read(&mm->mmap_sem);
>  	vma = find_vma_prev(mm, address, &prev_vma);
> @@ -201,6 +199,9 @@ good_area:
>  	if ((vma->vm_flags & acc_type) != acc_type)
>  		goto bad_area;
>  
> +	if (acc_type & VM_WRITE)
> +		flags |= FAULT_FLAG_WRITE;

Can acc_type actually change between between the first round and a
retry?  Otherwise, it might make sense to pull this up and place it
next to the flag initialization instead of pulling one flag down.
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