Increasing MAXLOGNAME from 17 to 33

[Warner Losh]

On Nov 13, 2012, at 3:59 PM, Baptiste Daroussin wrote:

> On Tue, Nov 13, 2012 at 08:45:12PM +0200, Konstantin Belousov wrote:
>> On Tue, Nov 13, 2012 at 08:42:38PM +0200, Konstantin Belousov wrote:
>>> On Tue, Nov 13, 2012 at 07:34:12PM +0100, Baptiste Daroussin wrote:
>>>> On Tue, Nov 13, 2012 at 01:50:34PM +0200, Konstantin Belousov wrote:
>>>>> On Tue, Nov 13, 2012 at 12:18:06PM +0100, Baptiste Daroussin wrote:
>>>>>> Hi,
>>>>>> 
>>>>>> I want to increase MAXLOGNAME in sys/param.h from 17 to 33 to allow 32-character
>>>>>> long usernames, the PR: misc/161091 and misc/133926 already requested for it.
>>>>>> 
>>>>>> utmpx already allow 32 character long user names.
>>>>>> 
>>>>>> I plan to bump the __FreeBSD_version at the same time because of the ABI
>>>>>> breakage.
>>>>>> 
>>>>>> This is simplify life of lots administrator, this value, is a common value for
>>>>>> other operating systems.
>>>>>> 
>>>>>> Do anyone have objections about it?
>>>>> 
>>>>> Yes, I have. Do not break the ABI, it is plain prohibited.
>>>>> You might consider increasing the constant only if providing ABI
>>>>> compatibility shims.
>>>>> 
>>>>> In fact, the cursory look over the whole base system indicates that ABI
>>>>> breakage might be not that big and could be mitigated with relatively
>>>>> limited amount of the efforts.
>>>> 
>>>> Thanks cognet for the help on the following.
>>>> 
>>>> After auditing base, it seems like this patch is enough
>>>> http://people.freebsd.org/~bapt/maxlogname-33.diff
>>> Regarding the patch, the dereferencing of p->p_session should be done
>>> under the proc lock to guarantee stability of p_pgrp, and under session
>>> mutex to prevent s_login modifications. Altogether, this means that the
>>> if() shall be moved down right before bcopy and locks unlocked on return.
>>> 
>> Sorry, sent the reply too early.
>> 
>> The alternative is to check for the length of the local 'login' variable
>> after unlocks, right before copyout.
>> 
> like this?
> http://people.freebsd.org/~bapt/report-erange-if-login-is-larger-then-MAXLOGNAME.diff

Isn't that check too late?

Warner