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Message-ID: <c9ef2b56eaf36c8e5449b751ab6e5971b6b34311.camel@perches.com>
Date: Tue, 23 Jul 2019 08:39:49 -0700
From: Joe Perches <joe@...ches.com>
To: Rasmus Villemoes <linux@...musvillemoes.dk>, Linus Torvalds
<torvalds@...ux-foundation.org>, linux-kernel@...r.kernel.org
Cc: Jonathan Corbet <corbet@....net>, Stephen Kitt <steve@....org>, Kees
Cook <keescook@...omium.org>, Nitin Gote <nitin.r.gote@...el.com>,
jannh@...gle.com, kernel-hardening@...ts.openwall.com, Andrew Morton
<akpm@...ux-foundation.org>
Subject: Re: [PATCH V2 1/2] string: Add stracpy and stracpy_pad mechanisms
On Tue, 2019-07-23 at 16:37 +0200, Rasmus Villemoes wrote:
> On 23/07/2019 15.51, 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 (dest) and uses sizeof(dest) as the
> > count of bytes to copy.
> >
> > These mechanisms verify that the dest argument is an array of
> > char or other compatible types like u8 or s8 or equivalent.
> Sorry, but "compatible types" has a very specific meaning in C, so
> please don't use that word.
I think you are being overly pedantic here but
what wording do you actually suggest?
> And yes, the kernel disables -Wpointer-sign,
> so passing an u8* or s8* when strscpy() expects a char* is silently
> accepted, but does such code exist?
u8 definitely, s8 I'm not sure.
I don't find via grep a use of s8 foo[] = "bar";
or "signed char foo[] = "bar";
I don't think it bad to allow it.
> > V2: Use __same_type testing char[], signed char[], and unsigned char[]
> > Rename to, from, and size, dest, src and count
>
> count is just as bad as size in terms of "the expression src might
> contain that identifier". But there's actually no reason to even declare
> a local variable, just use ARRAY_SIZE() directly as the third argument
> to strscpy().
I don't care about that myself.
It's a macro local identifier and shadowing in a macro
is common. I'm not a big fan of useless underscores.
I think either works.
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