linux-kernel - RE: [PATCH 1/1] crypto: If two strings are exact match, they must have same length.

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Date:   Mon, 27 Mar 2017 23:04:30 +0000
From:   "Ming Ma (mingma)" <mingma@...ron.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
CC:     "davem@...emloft.net" <davem@...emloft.net>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH 1/1] crypto: If two strings are exact match, they must
 have same length.

Please ignore this patch, we have seen some issues in older verison of linux kernel. But it doesn't seem to be an issue in the latest kernel.

thanks

-----Original Message-----
From: linux-crypto-owner@...r.kernel.org [mailto:linux-crypto-owner@...r.kernel.org] On Behalf Of Herbert Xu
Sent: Tuesday, March 21, 2017 8:01 PM
To: Ming Ma (mingma) <mingma@...ron.com>
Cc: davem@...emloft.net; linux-crypto@...r.kernel.org; linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] crypto: If two strings are exact match, they must have same length.

On Tue, Mar 21, 2017 at 04:40:40PM -0500, Ming Ma wrote:
> When both "crct10dif-pclmul" algorithm and "crct10dif-generic" 
> algorithm exist in crypto_alg_list, "crct10dif-pclmul" should be 
> selected, since it has higher priority than "crct10dif-generic". 
> However, both algorithms have the same cra_name "crct10dif". If we use 
> "crct10dif" to find a matched algorithm in crypto_alg_list, it's 
> possible "crct10dif-generic" is selected, because the code calls 
> strcmp to decide if two string are exact match, but doesn't check if two strings have the same length.
> 
> exact = !strcmp(q->cra_driver_name, name);
> 
> So ,if "crct10dif-generic" is in front of "crct10dif-pclmul" in 
> crypto_alg_list, it will be picked as the matched algorithm, even if 
> it has lower priority than "crct10dif-pclmul".
> Signed-off-by: Ming Ma <mingma@...ron.com>
> ---
>  crypto/api.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/crypto/api.c b/crypto/api.c index b16ce16..5b3d45a 100644
> --- a/crypto/api.c
> +++ b/crypto/api.c
> @@ -76,7 +76,8 @@ static struct crypto_alg *__crypto_alg_lookup(const char *name, u32 type,
>  		    ((struct crypto_larval *)q)->mask != mask)
>  			continue;
>  
> -		exact = !strcmp(q->cra_driver_name, name);
> +		exact = (strlen(name) == strlen(q->cra_driver_name)) &&
> +				!strcmp(q->cra_driver_name, name);
>  		fuzzy = !strcmp(q->cra_name, name);
>  		if (!exact && !(fuzzy && q->cra_priority > best))
>  			continue;

This is bogus.  Please describe how you reproduced the problem.

The priority matching should work.

Cheers,
--
Email: Herbert Xu <herbert@...dor.apana.org.au> Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt