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    SubjectRe: [RFC PATCH] string.h: Add stracpy/stracpy_pad (was: Re: [PATCH] checkpatch: Added warnings in favor of strscpy().)
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    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); \
    > > > +})
    > > > +
    > > > +#define stracpy_pad(to, from) \
    > > > +({ \
    > > > + size_t size = ARRAY_SIZE(to); \
    > > > + BUILD_BUG_ON(!__same_type(typeof(*to), char)); \
    > > > + \
    > > > + strscpy_pad(to, from, size); \
    > > > +})
    > > > +
    > > > #ifndef __HAVE_ARCH_STRCAT
    > > > extern char * strcat(char *, const char *);
    > > > #endif
    > >
    > > This seems like a reasonable addition, yes. I think Coccinelle might
    > > actually be able to find all the existing strscpy(dst, src, sizeof(dst))
    > > cases to jump-start this conversion.
    >
    > I did that. It works. It's a lot of conversions.
    >
    > $ cat str.cpy.cocci
    > @@
    > expression e1;
    > expression e2;
    > @@
    >
    > - strscpy(e1, e2, sizeof(e1))
    > + stracpy(e1, e2)
    >
    > @@
    > expression e1;
    > expression e2;
    > @@
    >
    > - strlcpy(e1, e2, sizeof(e1))
    > + stracpy(e1, e2)
    >
    > > Devil's advocate: this adds yet more string handling functions... will
    > > this cause even more confusion?
    >
    > Documentation is good.
    > Actual in-kernel use and examples better.

    btw: I just ran this again and it produces:

    $ spatch --in-place -sp-file str.cpy.cocci .
    $ git checkout tools/
    $ git diff --shortstat
    958 files changed, 2179 insertions(+), 2655 deletions(-)


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