linux-kernel - [RFC PATCH] string.h: Add stracpy/stracpy_pad (was: Re: [PATCH] checkpatch: Added warnings in favor of strscpy().)

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Message-ID: <d1524130f91d7cfd61bc736623409693d2895f57.camel@perches.com>
Date:   Thu, 04 Jul 2019 17:15:57 -0700
From:   Joe Perches <joe@...ches.com>
To:     Nitin Gote <nitin.r.gote@...el.com>, akpm@...ux-foundation.org
Cc:     corbet@....net, apw@...onical.com, keescook@...omium.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-hardening@...ts.openwall.com
Subject: [RFC PATCH] string.h: Add stracpy/stracpy_pad (was: Re: [PATCH]
 checkpatch: Added warnings in favor of strscpy().)

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