linux-kernel - [PATCH 1/8] purgatory/sha256: replace memset by memzero

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Message-Id: <1417366774-32412-2-git-send-email-Julia.Lawall@lip6.fr>
Date:	Sun, 30 Nov 2014 17:59:27 +0100
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	dborkman@...hat.com, herbert@...dor.apana.org.au,
	kernel-janitors@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Julia Lawall <julia@...u.dk>
Subject: [PATCH 1/8] purgatory/sha256: replace memset by memzero_explicit

From: Julia Lawall <julia@...u.dk>

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@...u.dk>

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

 arch/x86/purgatory/sha256.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/purgatory/sha256.c b/arch/x86/purgatory/sha256.c
index 548ca67..8271ca5 100644
--- a/arch/x86/purgatory/sha256.c
+++ b/arch/x86/purgatory/sha256.c
@@ -205,7 +205,7 @@ static void sha256_transform(u32 *state, const u8 *input)
 
 	/* clear any sensitive info... */
 	a = b = c = d = e = f = g = h = t1 = t2 = 0;
-	memset(W, 0, 64 * sizeof(u32));
+	memzero_explicit(W, 64 * sizeof(u32));
 }
 
 int sha256_init(struct sha256_state *sctx)

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