linux-kernel - Re: [PATCH 7/9] sys: Replace hardcoding of -20 and 19 with MIN_NICE and MAX

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Message-ID: <CAGXu5jKqEF7KPk0MipmcSB_5=Ka3RfehKS7gceFjUaOyMQSeng@mail.gmail.com>
Date:	Tue, 11 Feb 2014 22:40:32 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Dongsheng Yang <yangds.fnst@...fujitsu.com>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Oleg Nesterov <oleg@...hat.com>, Robin Holt <holt@....com>,
	Al Viro <viro@...iv.linux.org.uk>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [PATCH 7/9] sys: Replace hardcoding of -20 and 19 with MIN_NICE
 and MAX_NICE.

On Tue, Feb 11, 2014 at 7:59 PM, Dongsheng Yang
<yangds.fnst@...fujitsu.com> wrote:
> Hi Kees,
>
>
>  On 02/12/2014 02:27 AM, Kees Cook wrote:
>>
>> On Mon, Feb 10, 2014 at 11:34 PM, Dongsheng Yang
>> <yangds.fnst@...fujitsu.com> wrote:
>>>
>>> Signed-off-by: Dongsheng Yang <yangds.fnst@...fujitsu.com>
>>> cc: Andrew Morton <akpm@...ux-foundation.org>
>>> cc: Oleg Nesterov <oleg@...hat.com>
>>> cc: Robin Holt <holt@....com>
>>> cc: Al Viro <viro@...iv.linux.org.uk>
>>> cc: Kees Cook <keescook@...omium.org>
>>> cc: "Eric W. Biederman" <ebiederm@...ssion.com>
>>> cc: Stephen Rothwell <sfr@...b.auug.org.au>
>>> cc: Peter Zijlstra <peterz@...radead.org>
>>> cc: Ingo Molnar <mingo@...nel.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);
>
>
> Good suggestion! This patch here is just to replace the numeric values with
> a name defined in prio.h. So I will send another patch to make it more
> readable
> with clamp after the patch set here applied. Is this plan ok to you?

Sounds good to me. Thanks!

-Kees

>
> Thanx.
>
>>
>> -Kees
>>
>>>          rcu_read_lock();
>>>          read_lock(&tasklist_lock);
>>> --
>>> 1.8.2.1
>>>
>>
>>
>



-- 
Kees Cook
Chrome OS Security
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