RE: [PATCH v5] Documentation/checkpatch: Prefer strscpy/strscpy_pad over strcpy/strlcpy/strncpy

["Gote, Nitin R" <nitin.r.gote@intel.com>]

> -----Original Message-----
> From: Joe Perches [mailto:joe@perches.com]
> Sent: Monday, July 22, 2019 11:11 PM
> To: Kees Cook <keescook@chromium.org>; Gote, Nitin R
> <nitin.r.gote@intel.com>
> Cc: corbet@lwn.net; akpm@linux-foundation.org; apw@canonical.com;
> linux-doc@vger.kernel.org; kernel-hardening@lists.openwall.com
> Subject: Re: [PATCH v5] Documentation/checkpatch: Prefer
> strscpy/strscpy_pad over strcpy/strlcpy/strncpy
> 
> On Mon, 2019-07-22 at 10:30 -0700, Kees Cook wrote:
> > On Wed, Jul 17, 2019 at 10:00:05AM +0530, NitinGote wrote:
> > > From: Nitin Gote <nitin.r.gote@intel.com>
> > >
> > > Added check in checkpatch.pl 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.
> > >
> > > Signed-off-by: Nitin Gote <nitin.r.gote@intel.com>
> >
> > Reviewed-by: Kees Cook <keescook@chromium.org>
> >
> > Joe, does this address your checkpatch concerns?
> 
> Well, kinda.
> 
> strscpy_pad isn't used anywhere in the kernel.
> 
> And
> 
> +        "strncpy"				=> "strscpy, strscpy_pad or for non-
> NUL-terminated strings, strncpy() can still be used, but destinations should
> be marked with __nonstring",
> 
> is a bit verbose.  This could be simply:
> 
> +        "strncpy" => "strscpy - for non-NUL-terminated uses, strncpy() dst
> should be __nonstring",
> 

But, if the destination buffer needs extra NUL-padding for remaining size of destination, 
then safe replacement is strscpy_pad().  Right?  If yes, then what is your opinion on below change :

        "strncpy" => "strscpy, strcpy_pad - for non-NUL-terminated uses, strncpy() dst
should be __nonstring",


> And I still prefer adding stracpy as it
> reduces code verbosity and eliminates defects.
> 

-Nitin