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Date: Tue, 11 Feb 2014 10:27:48 -0800
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Subject: Re: [PATCH 7/9] sys: Replace hardcoding of -20 and 19 with MIN_NICE
 and MAX_NICE.
From: Kees Cook <keescook@chromium.org>
To: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
Cc: LKML <linux-kernel@vger.kernel.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, Robin Holt <holt@sgi.com>,
        Al Viro <viro@zeniv.linux.org.uk>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Stephen Rothwell <sfr@canb.auug.org.au>,
        Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@kernel.org>
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On Mon, Feb 10, 2014 at 11:34 PM, Dongsheng Yang
<yangds.fnst@cn.fujitsu.com> wrote:
> Signed-off-by: Dongsheng Yang <yangds.fnst@cn.fujitsu.com>
> cc: Andrew Morton <akpm@linux-foundation.org>
> cc: Oleg Nesterov <oleg@redhat.com>
> cc: Robin Holt <holt@sgi.com>
> cc: Al Viro <viro@zeniv.linux.org.uk>
> cc: Kees Cook <keescook@chromium.org>
> cc: "Eric W. Biederman" <ebiederm@xmission.com>
> cc: Stephen Rothwell <sfr@canb.auug.org.au>
> cc: Peter Zijlstra <peterz@infradead.org>
> cc: Ingo Molnar <mingo@kernel.org>
> ---
>  kernel/sys.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sys.c b/kernel/sys.c
> index c0a58be..adaeab6 100644
> --- a/kernel/sys.c
> +++ b/kernel/sys.c
> @@ -174,10 +174,10 @@ SYSCALL_DEFINE3(setpriority, int, which, int, who, int, niceval)
>
>         /* normalize: avoid signed division (rounding problems) */
>         error = -ESRCH;
> -       if (niceval < -20)
> -               niceval = -20;
> -       if (niceval > 19)
> -               niceval = 19;
> +       if (niceval < MIN_NICE)
> +               niceval = MIN_NICE;
> +       if (niceval > MAX_NICE)
> +               niceval = MAX_NICE;

Good catch! I'm all for using names instead of numeric values,
however, I wonder if it'd be more readable to use "clamp" instead?

niceval = clamp(niceval, MIN_NICE, MAX_NICE);

-Kees

>
>         rcu_read_lock();
>         read_lock(&tasklist_lock);
> --
> 1.8.2.1
>



-- 
Kees Cook
Chrome OS Security