linux-kernel - Re: [PATCH] crypto: Add a flag allowing the self-tests to be disabled at runtime.

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Date:	Fri, 29 Apr 2016 12:59:57 +0200
From:	Stephan Mueller <sm@...rm.de>
To:	"Richard W.M. Jones" <rjones@...hat.com>
Cc:	linux-kernel@...r.kernel.org, corbet@....net,
	herbert@...dor.apana.org.au, davem@...emloft.net,
	linux-doc@...r.kernel.org, linux-crypto@...r.kernel.org
Subject: Re: [PATCH] crypto: Add a flag allowing the self-tests to be disabled at runtime.

Am Freitag, 29. April 2016, 11:07:43 schrieb Richard W.M. Jones:

Hi Richard,

> Running self-tests for a short-lived KVM VM takes 28ms on my laptop.
> This commit adds a flag 'cryptomgr.notests' which allows them to be
> disabled.
> 
> Signed-off-by: Richard W.M. Jones <rjones@...hat.com>
> ---
>  Documentation/kernel-parameters.txt | 3 +++
>  crypto/testmgr.c                    | 9 +++++++++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/Documentation/kernel-parameters.txt
> b/Documentation/kernel-parameters.txt index 0b3de80..d4d5fb7 100644
> --- a/Documentation/kernel-parameters.txt
> +++ b/Documentation/kernel-parameters.txt
> @@ -826,6 +826,9 @@ bytes respectively. Such letter suffixes can also be
> entirely omitted. It will be ignored when crashkernel=X,high is not used
>  			or memory reserved is below 4G.
> 
> +	cryptomgr.notests
> +                        [KNL] Disable crypto self-tests
> +
>  	cs89x0_dma=	[HW,NET]
>  			Format: <dma>
> 
> diff --git a/crypto/testmgr.c b/crypto/testmgr.c
> index b86883a..dc613f2 100644
> --- a/crypto/testmgr.c
> +++ b/crypto/testmgr.c
> @@ -35,6 +35,10 @@
> 
>  #include "internal.h"
> 
> +static bool notests;
> +module_param(notests, bool, 0644);
> +MODULE_PARM_DESC(notests, "disable crypto self-tests");
> +
>  #ifdef CONFIG_CRYPTO_MANAGER_DISABLE_TESTS
> 
>  /* a perfect nop */
> @@ -3868,6 +3872,11 @@ int alg_test(const char *driver, const char *alg, u32
> type, u32 mask) int j;
>  	int rc;
> 
> +	if (notests) {

What about if (!fips_enabled && notests) ?

I am not sure whether the kernel should prevent mistakes in user space. A 
mistake would be when setting fips=1 and notests=1 as the FIPS mode mandates 
the self tests.

> +		pr_info("alg: self-tests disabled\n");
> +		return 0;
> +	}
> +
>  	alg_test_descs_check_order();
> 
>  	if ((type & CRYPTO_ALG_TYPE_MASK) == CRYPTO_ALG_TYPE_CIPHER) {


Ciao
Stephan
-- 
| Nimm das Recht weg -                                             |
|  was ist dann der Staat noch anderes als eine große Räuberbande? |