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[198.145.64.163]) by smtp.gmail.com with ESMTPSA id v184sm38171686pgd.34.2019.07.22.11.21.30 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 22 Jul 2019 11:21:30 -0700 (PDT) Date: Mon, 22 Jul 2019 11:21:29 -0700 From: Kees Cook To: Joe Perches Cc: Nitin Gote , 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 Subject: Re: [RFC PATCH] string.h: Add stracpy/stracpy_pad (was: Re: [PATCH] checkpatch: Added warnings in favor of strscpy().) Message-ID: <201907221119.9ECF3466@keescook> References: <1562219683-15474-1-git-send-email-nitin.r.gote@intel.com> <201907221031.8B87A9DE@keescook> <2c959c56c23d0052e5c35ecfa2f6051b17fb2798.camel@perches.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2c959c56c23d0052e5c35ecfa2f6051b17fb2798.camel@perches.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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); \ > > > > +}) > > > > + > > > > +#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(-) Cool. Well, assuming no one hates this, let's do it. :) Can you send a more complete patch with docs, etc? Maybe Linus will take it for late in the next merge window, perhaps? -- Kees Cook