From: Stefan Rompf <stefan@loplof.de>
To: Arjan van de Ven <arjan@infradead.org>
Subject: Re: [Patch 2.6] dm-crypt: zero key before freeing it
Date: Wed, 4 Jan 2006 21:26:46 +0100
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Am Mittwoch 04 Januar 2006 21:09 schrieb Arjan van de Ven:

> since a memset right before a free is a very unusual code pattern in the
> kernel it may well be worth putting a short comment around it to prevent
> someone later removing it as "optimization"

Valid objection, here is an update (and see, I'm running 2.6.15 now ;-)

Stefan


Signed-off-by: Stefan Rompf <stefan@loplof.de>
Acked-by: Clemens Fruhwirth <clemens@endorphin.org>

--- linux-2.6.15/drivers/md/dm-crypt.c.orig	2006-01-04 01:01:16.000000000 +0100
+++ linux-2.6.15/drivers/md/dm-crypt.c	2006-01-04 21:23:34.000000000 +0100
@@ -690,6 +690,8 @@
 bad2:
 	crypto_free_tfm(tfm);
 bad1:
+	/* Must zero key material before freeing */
+	memset(cc, 0, sizeof(*cc) + cc->key_size * sizeof(u8));
 	kfree(cc);
 	return -EINVAL;
 }
@@ -706,6 +708,9 @@
 		cc->iv_gen_ops->dtr(cc);
 	crypto_free_tfm(cc->tfm);
 	dm_put_device(ti, cc->dev);
+
+	/* Must zero key material before freeing */
+	memset(cc, 0, sizeof(*cc) + cc->key_size * sizeof(u8));
 	kfree(cc);
 }
 
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