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Date:   Mon, 22 Jul 2019 11:27:04 -0700
From:   Matthew Wilcox <willy@infradead.org>
To:     Joe Perches <joe@perches.com>
Cc:     Kees Cook <keescook@chromium.org>,
        Nitin Gote <nitin.r.gote@intel.com>, akpm@linux-foundation.org,
        corbet@lwn.net, apw@canonical.com, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, kernel-hardening@lists.openwall.com,
        Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Subject: Re: [RFC PATCH] string.h: Add stracpy/stracpy_pad (was: Re: [PATCH]
 checkpatch: Added warnings in favor of strscpy().)
Message-ID: <20190722182703.GE363@bombadil.infradead.org>
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On Mon, Jul 22, 2019 at 10:58:15AM -0700, Joe Perches wrote:
> On Mon, 2019-07-22 at 10:43 -0700, Joe Perches wrote:
> > On Mon, 2019-07-22 at 10:33 -0700, Kees Cook wrote:
> > > On Thu, Jul 04, 2019 at 05:15:57PM -0700, Joe Perches wrote:
> > > > On Thu, 2019-07-04 at 13:46 -0700, Joe Perches wrote:
> > > > > On Thu, 2019-07-04 at 11:24 +0530, Nitin Gote wrote:
> > > > > > Added warnings in checkpatch.pl script to :
> > > > > > 
> > > > > > 1. Deprecate strcpy() in favor of strscpy().
> > > > > > 2. Deprecate strlcpy() in favor of strscpy().
> > > > > > 3. Deprecate strncpy() in favor of strscpy() or strscpy_pad().
> > > > > > 
> > > > > > Updated strncpy() section in Documentation/process/deprecated.rst
> > > > > > to cover strscpy_pad() case.
> > > > 
> > > > []
> > > > 
> > > > I sent a patch series for some strscpy/strlcpy misuses.
> > > > 
> > > > How about adding a macro helper to avoid the misuses like:
> > > > ---
> > > >  include/linux/string.h | 16 ++++++++++++++++
> > > >  1 file changed, 16 insertions(+)
> > > > 
> > > > diff --git a/include/linux/string.h b/include/linux/string.h
> > > > index 4deb11f7976b..ef01bd6f19df 100644
> > > > --- a/include/linux/string.h
> > > > +++ b/include/linux/string.h
> > > > @@ -35,6 +35,22 @@ ssize_t strscpy(char *, const char *, size_t);
> > > >  /* Wraps calls to strscpy()/memset(), no arch specific code required */
> > > >  ssize_t strscpy_pad(char *dest, const char *src, size_t count);
> > > >  
> > > > +#define stracpy(to, from)					\
> > > > +({								\
> > > > +	size_t size = ARRAY_SIZE(to);				\
> > > > +	BUILD_BUG_ON(!__same_type(typeof(*to), char));		\
> > > > +								\
> > > > +	strscpy(to, from, size);				\
> > > > +})

Where does the 'a' in 'stracpy' come from?  Googling around finds other
people using a function called stracpy, but it takes different arguments.
http://stracpy.blogspot.com/ takes a size argument, as does
https://docs.polserver.com/doxygen/html/d5/dce/stracpy_8cpp_source.html

The one in the 'Links' webbrowser (can't find a link to its source) seems
like a strdup clone.