Re: [Patch 2.6] dm-crypt: zero key before freeing it

[Phillip Susi <psusi@cfl.rr.com>]

Once the page is placed on the free list, doesn't that prevent it from 
being swapped out?  swsusp doesn't bother saving free pages and before 
the pages can be recycled, the kernel zeros them right?

Stefan Rompf wrote:
> Hi Andrew,
>
> dm-crypt does not clear struct crypt_config before freeing it. Thus, 
> information on the key could leak f.e. to a swsusp image even after the 
> encrypted device has been removed. The attached patch against 2.6.14 / 2.6.15 
> fixes it.
>
> Signed-off-by: Stefan Rompf <stefan@loplof.de>
> Acked-by: Clemens Fruhwirth <clemens@endorphin.org>
>
> --- linux-2.6.14.4/drivers/md/dm-crypt.c.old	2005-12-16 18:27:05.000000000 +0100
> +++ linux-2.6.14.4/drivers/md/dm-crypt.c	2005-12-28 12:49:13.000000000 +0100
> @@ -694,6 +694,7 @@ bad3:
>  bad2:
>  	crypto_free_tfm(tfm);
>  bad1:
> +	memset(cc, 0, sizeof(*cc) + cc->key_size * sizeof(u8));
>  	kfree(cc);
>  	return -EINVAL;
>  }
> @@ -710,6 +711,7 @@ static void crypt_dtr(struct dm_target *
>  		cc->iv_gen_ops->dtr(cc);
>  	crypto_free_tfm(cc->tfm);
>  	dm_put_device(ti, cc->dev);
> +	memset(cc, 0, sizeof(*cc) + cc->key_size * sizeof(u8));
>  	kfree(cc);
>  }
>  
>
> -
>
>