linux-kernel - [PATCH 3/8 v2] crypto: replace memset by memzero

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Date:	Sun, 30 Nov 2014 18:03:44 +0100
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	kernel-janitors@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 3/8 v2] crypto: replace memset by memzero_explicit

From: Julia Lawall <Julia.Lawall@...6.fr>

Memset on a local variable may be removed when it is called just before the
variable goes out of scope.  Using memzero_explicit defeats this
optimization.  A simplified version of the semantic patch that makes this
change is as follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
identifier x;
type T;
@@

{
... when any
T x[...];
... when any
    when exists
- memset
+ memzero_explicit
  (x,
-0,
  ...)
... when != x
    when strict
}
// </smpl>

This change was suggested by Daniel Borkmann <dborkman@...hat.com>

Signed-off-by: Julia Lawall <Julia.Lawall@...6.fr>

---
Daniel Borkmann suggested that these patches could go through Herbert Xu's
cryptodev tree.

v2: fixed email address

 arch/x86/crypto/sha256_ssse3_glue.c |    2 +-
 arch/x86/crypto/sha512_ssse3_glue.c |    2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/crypto/sha512_ssse3_glue.c b/arch/x86/crypto/sha512_ssse3_glue.c
index 26a5898..0b6af26 100644
--- a/arch/x86/crypto/sha512_ssse3_glue.c
+++ b/arch/x86/crypto/sha512_ssse3_glue.c
@@ -219,7 +219,7 @@ static int sha384_ssse3_final(struct shash_desc *desc, u8 *hash)
 	sha512_ssse3_final(desc, D);
 
 	memcpy(hash, D, SHA384_DIGEST_SIZE);
-	memset(D, 0, SHA512_DIGEST_SIZE);
+	memzero_explicit(D, SHA512_DIGEST_SIZE);
 
 	return 0;
 }
diff --git a/arch/x86/crypto/sha256_ssse3_glue.c b/arch/x86/crypto/sha256_ssse3_glue.c
index 4dc100d..8fad72f 100644
--- a/arch/x86/crypto/sha256_ssse3_glue.c
+++ b/arch/x86/crypto/sha256_ssse3_glue.c
@@ -211,7 +211,7 @@ static int sha224_ssse3_final(struct shash_desc *desc, u8 *hash)
 	sha256_ssse3_final(desc, D);
 
 	memcpy(hash, D, SHA224_DIGEST_SIZE);
-	memset(D, 0, SHA256_DIGEST_SIZE);
+	memzero_explicit(D, SHA256_DIGEST_SIZE);
 
 	return 0;
 }

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