linux-kernel - [PATCH 5/8] dm: replace memset by memzero

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Date:	Sun, 30 Nov 2014 17:59:31 +0100
From:	Julia Lawall <Julia.Lawall@...6.fr>
To:	Alasdair Kergon <agk@...hat.com>
Cc:	dborkman@...hat.com, herbert@...dor.apana.org.au,
	kernel-janitors@...r.kernel.org, Mike Snitzer <snitzer@...hat.com>,
	dm-devel@...hat.com, Neil Brown <neilb@...e.de>,
	linux-raid@...r.kernel.org, linux-kernel@...r.kernel.org,
	Julia Lawall <julia@...u.dk>
Subject: [PATCH 5/8] dm: 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.

 drivers/md/dm-crypt.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index fc93b93..08981be 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -705,7 +705,7 @@ static int crypt_iv_tcw_whitening(struct crypt_config *cc,
 	for (i = 0; i < ((1 << SECTOR_SHIFT) / 8); i++)
 		crypto_xor(data + i * 8, buf, 8);
 out:
-	memset(buf, 0, sizeof(buf));
+	memzero_explicit(buf, sizeof(buf));
 	return r;
 }
 

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