linux-kernel - Re: [PATCH 1/2] tty: ldisc: Fix misuse of proc_dointvec "ldisc

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Date:   Tue, 25 Jun 2019 13:40:05 +0900
From:   Eiichi Tsukata <devel@...ukata.com>
To:     Greg KH <gregkh@...uxfoundation.org>
Cc:     jslaby@...e.com, davem@...emloft.net, kuznet@....inr.ac.ru,
        yoshfuji@...ux-ipv6.org, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] tty: ldisc: Fix misuse of proc_dointvec
 "ldisc_autoload"



On 2019/06/25 12:32, Greg KH wrote:
> On Tue, Jun 25, 2019 at 12:08:00PM +0900, Eiichi Tsukata wrote:
>> /proc/sys/dev/tty/ldisc_autoload assumes given value to be 0 or 1. Use
>> proc_dointvec_minmax instead of proc_dointvec.
>>
>> Fixes: 7c0cca7c847e "(tty: ldisc: add sysctl to prevent autoloading of ldiscs)"
>> Signed-off-by: Eiichi Tsukata <devel@...ukata.com>
>> ---
>>  drivers/tty/tty_ldisc.c | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/drivers/tty/tty_ldisc.c b/drivers/tty/tty_ldisc.c
>> index e38f104db174..a8ea7a35c94e 100644
>> --- a/drivers/tty/tty_ldisc.c
>> +++ b/drivers/tty/tty_ldisc.c
>> @@ -863,7 +863,7 @@ static struct ctl_table tty_table[] = {
>>  		.data		= &tty_ldisc_autoload,
>>  		.maxlen		= sizeof(tty_ldisc_autoload),
>>  		.mode		= 0644,
>> -		.proc_handler	= proc_dointvec,
>> +		.proc_handler	= proc_dointvec_minmax,
>>  		.extra1		= &zero,
>>  		.extra2		= &one,
> 
> Ah, nice catch.  But this really isn't an issue as if you use a bigger
> value, things will not "break", right?
> 

Someone may misuse -1 to disable ldisc autoload, but basically it does not
"break".

Thanks,

Eiichi