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Subject: Re: svn commit: r298420 - head/sys/geom
To: Alan Somers <asomers@freebsd.org>, Ngie Cooper <yaneurabeya@gmail.com>
References: <201604211643.u3LGhFpR057982@repo.freebsd.org>
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From: Hans Petter Selasky <hps@selasky.org>
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Date: Thu, 21 Apr 2016 19:33:55 +0200
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On 04/21/16 19:26, Alan Somers wrote:
> On Thu, Apr 21, 2016 at 11:09 AM, Ngie Cooper <yaneurabeya@gmail.com> wrote:
>
>> On Thu, Apr 21, 2016 at 10:08 AM, Ngie Cooper <yaneurabeya@gmail.com>
>> wrote:
>>> On Thu, Apr 21, 2016 at 9:43 AM, Alan Somers <asomers@freebsd.org>
>>>>   {
>>>>          struct g_geom *gp;
>>>>          struct g_provider *pp;
>>>> +       char devnamebuf[128];
>>>
>>> Why 128? Also, why not sbuf?
>>>
>>>>          gp = dp->d_geom;
>>>>          if (gp != NULL)
>>>>                  LIST_FOREACH(pp, &gp->provider, provider)
>>>>                          (void)g_attr_changed(pp, attr, flag);
>>>> +       snprintf(devnamebuf, 128, "devname=%s%d", dp->d_name,
>> dp->d_unit);
>>>
>>> Why not sizeof(devnamebuf) ?
>>
>> Also: this doesn't NUL terminate devnamebuf; it really should
>> (otherwise, boom... crash in geom)...
>>
>
> snprintf(3) says "The output is always null-terminated." and it looks like
> the kernel version does the same thing at subr_prf.c:560.  Am I missing
> something?
>

Hi,

The code is correct, though it is good practice to use sizeof() like 
Ngie suggests or define the size of the buffer like a macro.

grep -rE "snprintf.*sizeof" /usr/src/sys/dev

--HPS