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Date:   Mon, 3 Dec 2018 12:14:36 -0800
From:   Luis Chamberlain <mcgrof@kernel.org>
To:     cheng.lin130@zte.com.cn, keescook@chromium.org,
        akpm@linux-foundation.org, ebiederm@xmission.com
Cc:     linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
        zhong.weidong@zte.com.cn, wang.yi59@zte.com.cn
Subject: Re: Re: [PATCH] proc/sysctl: fix return error for
 proc_doulongvec_minmax
Message-ID: <20181203201436.GO28501@garbanzo.do-not-panic.com>
References: <20181130191456.GX18410@garbanzo.do-not-panic.com>
 <201812031312398404610@zte.com.cn>
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On Mon, Dec 03, 2018 at 01:12:39PM +0800, cheng.lin130@zte.com.cn wrote:
> >Cheng, thanks for the patch!
> >
> >On Fri, Nov 30, 2018 at 02:35:17PM +0800, Cheng Lin wrote:
> >> If the number of input parameters is less than the total
> >> parameters, an INVAL error will be returned.
> >
> >Do you mean EINVAL?
> >
> Yes, it's EINVAL.

Please adjust the commit log.

> >> This patch ensure no error returned in this condition, just
> >> like other interfaces do.
> >
> >Have an actual example to reproduce?
> >
> >Luis
> >
> We use proc_doulongvec_minmax to pass up to two parameters with kern_table.
> e.g. 
>         {
>                 .procname       = "monitor_signals",
>                 .data           = &monitor_sigs,
>                 .maxlen         = 2*sizeof(unsigned long),
>                 .mode           = 0644,
>                 .proc_handler   = proc_doulongvec_minmax,
>         },
> 
> Reproduce:
> When passing two parameters, it's work normal. But passing only one parameter, an error "Invalid argument"(EINVAL) is returned.
> [root@cl150 ~]# echo 1 2 > /proc/sys/kernel/monitor_signals
> [root@cl150 ~]# cat /proc/sys/kernel/monitor_signals
> 1       2
> [root@cl150 ~]# echo 3 > /proc/sys/kernel/monitor_signals
> -bash: echo: write error: Invalid argument
> [root@cl150 ~]# echo $?
> 1
> [root@cl150 ~]# cat /proc/sys/kernel/monitor_signals
> 3       2
> [root@cl150 ~]#
> 
> The following is the result after apply this patch. No error is returned when the number of input parameters is less than the total parameters.
> [root@cl150 ~]# echo 1 2 > /proc/sys/kernel/monitor_signals
> [root@cl150 ~]# cat /proc/sys/kernel/monitor_signals
> 1       2
> [root@cl150 ~]# echo 3 > /proc/sys/kernel/monitor_signals
> [root@cl150 ~]# echo $?
> 0
> [root@cl150 ~]# cat /proc/sys/kernel/monitor_signals
> 3       2
> [root@cl150 ~]#

This would be good to have in the commit log as well. But your patch
only addresses one of the proc users, there are a few other checks like
this that would also need to be expanded for this. So please expand
your patch to cover the other cases as well.

Since this worked before I do agree that we need to keep it working now,
and I can't think of an issue with returning 0 now. Since this is about
semantics though I'd like a bit more review from at last one more
person.

Kees, Eric, Andrew?

  Luis

> Cheng
> 
> >> Signed-off-by: Cheng Lin <cheng.lin130@zte.com.cn>
> >> ---
> >>  kernel/sysctl.c | 2 ++
> >>  1 file changed, 2 insertions(+)
> >>
> >> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> >> index 5fc724e..9ee261f 100644
> >> --- a/kernel/sysctl.c
> >> +++ b/kernel/sysctl.c
> >> @@ -2779,6 +2779,8 @@ static int __do_proc_doulongvec_minmax(void *data, struct ctl_table *table, int
> >>              bool neg;
> >>
> >>              left -= proc_skip_spaces(&p);
> >> +            if (!left)
> >> +                break;
> >>
> >>              err = proc_get_long(&p, &left, &val, &neg,
> >>                           proc_wspace_sep,
> >> --
> >> 1.8.3.1
> >>