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Message-ID: <9a5dedb0c9221743033f28974820e8dd724e388d.camel@perches.com>
Subject: Re: [PATCH 8/8] nfsd: Fix misuse of strlcpy
From:   Joe Perches <joe@perches.com>
To:     "J. Bruce Fields" <bfields@fieldses.org>
Cc:     Chuck Lever <chuck.lever@oracle.com>, linux-nfs@vger.kernel.org,
        linux-kernel@vger.kernel.org
Date:   Mon, 08 Jul 2019 22:40:50 -0700
In-Reply-To: <20190709031404.GD14439@fieldses.org>
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         <b51141d12de77eb22101e81f9eb2c9cc44104d7a.1562283944.git.joe@perches.com>
         <20190709031404.GD14439@fieldses.org>
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On Mon, 2019-07-08 at 23:14 -0400, J. Bruce Fields wrote:
> On Thu, Jul 04, 2019 at 04:57:48PM -0700, Joe Perches wrote:
> > Probable cut&paste typo - use the correct field size.
> 
> Huh, that's been there forever, I wonder why we haven't seen crashes?
> Oh, I see, name and authname both have the same size.
> 
> Anyway, makes sense, thanks.  Will apply for 5.3.
> 
> (Unless someone else is getting this; I didn't get copied on the rest of
> the series.)

It's generally hard to cc everyone on treewide fixes like this.

There's no good mechanism I know of.
vger mailing lists reject emails with too many addressees.

Do you have an opinion on adding the stracpy macro which
could avoid many of these defects?

---
 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