linux-kernel - Re: [PATCH] lib: string.c: Added a funktion function strzcpy

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Date:	Wed, 24 Sep 2014 18:41:42 +0300
From:	Dan Carpenter <dan.carpenter@...cle.com>
To:	Andi Kleen <ak@...ux.intel.com>
Cc:	Rickard Strandqvist <rickard_strandqvist@...ctrumdigital.se>,
	Grant Likely <grant.likely@...aro.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] lib: string.c:  Added a funktion function strzcpy

On Wed, Sep 24, 2014 at 07:35:55AM -0700, Andi Kleen wrote:
> On Wed, Sep 24, 2014 at 10:52:06AM +0300, Dan Carpenter wrote:
> > On Tue, Sep 23, 2014 at 06:17:53PM -0700, Andi Kleen wrote:
> > > On Wed, Sep 24, 2014 at 12:13:36AM +0200, Rickard Strandqvist wrote:
> > > > Added a function strzcpy which works the same as strncpy,
> > > > but guaranteed to produce the trailing null character.
> > > 
> > > Do we really need the bizarre strncpy padding semantics for anything?
> > > Why not just use strlcpy?
> > 
> > We do need the padding in many places to prevent information leaks.
> 
> Like where?
> 

You're asking what would break if we switched every strncpy() to
strlcpy() but it's not an easy question to answer.

I've looked a lot at information leaks, but strings are still a blind
spot for my Smatch.  My check only looks at normal variables, arrays.
Eventually I hope to fix this, of course.

I did a git search and Rickard has added some examples, but there were
definitely other places that rely strncpy() padding before.

regards,
dan carpenter

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