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From: Robert Watson <rwatson@FreeBSD.org>
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To: Mateusz Guzik <mjguzik@gmail.com>
Subject: Re: svn commit: r245036 - head/sys/kern
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
 src-committers@freebsd.org, David Xu <davidxu@FreeBSD.org>
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On Fri, 4 Jan 2013, Mateusz Guzik wrote:

> On Fri, Jan 04, 2013 at 11:11:13AM +0000, David Xu wrote:
>> Author: davidxu
>> Date: Fri Jan  4 11:11:12 2013
>> New Revision: 245036
>> URL: http://svnweb.freebsd.org/changeset/base/245036
>>
>> Log:
>>   Revert revision 244760 because strncpy pads trailing space with zero,
>>   this prevents kernel data from being leaked.
>
> I think it would be better to teach strlcpy to zero-pad as well.

I'd rather we created new functions with new names that add the non-portable 
zeroing behaviour -- perhaps strlpcpy() and strnpcpy(), or something equally 
incomprehensible.  This semantic may actually trigger bugs in code that is 
correct (albeit badly written) using strncpy() and strlcpy() in a way that 
never fully fills the buffer (due to some external invariant) and has an 
incorrect bounds check -- and potentially trigger performance problems when 
target buffers are much larger than the copied data.

Robert