linux-kernel - Re: [PATCH 1/2] string: Add stracpy and stracpy

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Message-ID: <b88ca439f5b2d578888a1cd39b30acb8121d422c.camel@perches.com>
Date:   Wed, 24 Jul 2019 04:40:30 -0700
From:   Joe Perches <joe@...ches.com>
To:     Kees Cook <keescook@...omium.org>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-kernel@...r.kernel.org, Jonathan Corbet <corbet@....net>,
        Stephen Kitt <steve@....org>,
        Nitin Gote <nitin.r.gote@...el.com>, jannh@...gle.com,
        kernel-hardening@...ts.openwall.com,
        Rasmus Villemoes <rasmus.villemoes@...vas.dk>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 1/2] string: Add stracpy and stracpy_pad mechanisms

On Tue, 2019-07-23 at 14:36 -0700, Kees Cook wrote:
> On Mon, Jul 22, 2019 at 05:38:15PM -0700, Joe Perches wrote:
> > Several uses of strlcpy and strscpy have had defects because the
> > last argument of each function is misused or typoed.
> > 
> > Add macro mechanisms to avoid this defect.
> > 
> > stracpy (copy a string to a string array) must have a string
> > array as the first argument (to) and uses sizeof(to) as the
> > size.
> > 
> > These mechanisms verify that the to argument is an array of
> > char or other compatible types like u8 or unsigned char.
> > 
> > A BUILD_BUG is emitted when the type of to is not compatible.
> > 
> > Signed-off-by: Joe Perches <joe@...ches.com>
> 
> I think Rasmus's suggestion would make sense:
> 
> 	BUILD_BUG_ON(!__same_type(typeof(to), char[]))

I think Rasmus had an excellent suggestion.
I liked it and submitted it as V2.

> Reviewed-by: Kees Cook <keescook@...omium.org>

Thanks.