linux-kernel - Re: [PATCH v3 1/9] crypto: introduce decompression API that can be called via sharable tfm object

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Message-ID: <20150921053859.GB5313@swordfish>
Date:	Mon, 21 Sep 2015 14:38:59 +0900
From:	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:	Joonsoo Kim <js1304@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Minchan Kim <minchan@...nel.org>,
	Nitin Gupta <ngupta@...are.org>,
	Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	Herbert Xu <herbert@...dor.apana.org.au>,
	"David S. Miller" <davem@...emloft.net>,
	Stephan Mueller <smueller@...onox.de>,
	Joonsoo Kim <iamjoonsoo.kim@....com>
Subject: Re: [PATCH v3 1/9] crypto: introduce decompression API that can be
 called via sharable tfm object

On (09/18/15 14:19), Joonsoo Kim wrote:
[..]
> @@ -61,7 +61,8 @@ static struct crypto_alg alg = {
>  	.cra_module		= THIS_MODULE,
>  	.cra_u			= { .compress = {
>  	.coa_compress		= crypto842_compress,
> -	.coa_decompress		= crypto842_decompress } }
> +	.coa_decompress		= crypto842_decompress,
> +	.coa_decompress_noctx	= NULL } }
>  };
>  
>  static int __init crypto842_mod_init(void)
> diff --git a/crypto/compress.c b/crypto/compress.c
> index c33f076..abb36a8 100644
> --- a/crypto/compress.c
> +++ b/crypto/compress.c
> @@ -33,12 +33,21 @@ static int crypto_decompress(struct crypto_tfm *tfm,
>  	                                                   dlen);
>  }
>  
> +static int crypto_decompress_noctx(struct crypto_tfm *tfm,
> +				const u8 *src, unsigned int slen,
> +				u8 *dst, unsigned int *dlen)
> +{
> +	return tfm->__crt_alg->cra_compress.coa_decompress_noctx(src, slen,
> +								dst, dlen);
> +}


hm... well... sorry, if irrelevant.
if the algorithm can have a _noctx() decompression function, does it
automatically guarantee that this algorithm never dereferences a passed
`struct crypto_tfm *tfm' pointer in its decompress function? in other words,
can we simply pass that `shared tfm pointer' to the existing decompress
function instead of defining new symbols, new callbacks, etc.?

	cot_decompress_noctx()  ==  cot_decompress(shared_ftm) ?

just a thought.

[..]
> +struct crypto_comp *crypto_alloc_comp_noctx(const char *alg_name,
> +					u32 type, u32 mask)
> +{
> +	struct crypto_comp *comp;
> +	struct crypto_tfm *tfm;
> +	struct compress_tfm *ops;
> +
> +	comp = crypto_alloc_comp(alg_name, type, mask);
> +	if (IS_ERR(comp))
> +		return comp;
> +
> +	tfm = crypto_comp_tfm(comp);
> +	if (!tfm->__crt_alg->cra_compress.coa_decompress_noctx) {
> +		crypto_free_comp(comp);
> +		return ERR_PTR(-EINVAL);

	-ENOMEM?

	-ss
--
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