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From: Julia Lawall <Julia.Lawall@lip6.fr>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: dborkman@redhat.com, herbert@gondor.apana.org.au,
        kernel-janitors@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org,
        linux-kernel@vger.kernel.org, Julia Lawall <julia@diku.dk>
Subject: [PATCH 1/8] purgatory/sha256: replace memset by memzero_explicit
Date: Sun, 30 Nov 2014 17:59:27 +0100
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From: Julia Lawall <julia@diku.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@redhat.com>

Signed-off-by: Julia Lawall <julia@diku.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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