linux-kernel - Re: [PATCH/RFC] mm, oom: Fix uninitialized ret in task_will_free

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Message-ID: <178c5e9b-b92d-b62b-40a9-ee98b10d6bce@I-love.SAKURA.ne.jp>
Date:	Thu, 4 Aug 2016 21:28:13 +0900
From:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
To:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Michal Hocko <mhocko@...e.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Oleg Nesterov <oleg@...hat.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH/RFC] mm, oom: Fix uninitialized ret in
 task_will_free_mem()

On 2016/08/04 5:19, Geert Uytterhoeven wrote:
>     mm/oom_kill.c: In function ‘task_will_free_mem’:
>     mm/oom_kill.c:767: warning: ‘ret’ may be used uninitialized in this function
> 
> If __task_will_free_mem() is never called inside the for_each_process()
> loop, ret will not be initialized.

Recently we are likely overlook this warning because newer versions (!?) do
not warn it. We need to try to compile using newer and older versions.

> 
> Fixes: 1af8bb43269563e4 ("mm, oom: fortify task_will_free_mem()")
> Signed-off-by: Geert Uytterhoeven <geert@...ux-m68k.org>
> ---
> Untested. I'm not familiar with the code, hence the default value of
> true was deducted from the logic in the loop (return false as soon as
> __task_will_free_mem() has returned false).

I think ret = true is correct. Andrew, please send to linux.git.

> ---
>  mm/oom_kill.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index 7d0a275df822e9e1..d53a9aa00977cbd0 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -764,7 +764,7 @@ bool task_will_free_mem(struct task_struct *task)
>  {
>  	struct mm_struct *mm = task->mm;
>  	struct task_struct *p;
> -	bool ret;
> +	bool ret = true;
>  
>  	/*
>  	 * Skip tasks without mm because it might have passed its exit_mm and
>