Re: [PATCH v2 1/4] crypto x86/sha1_mb: Fix load failure

[Rui Wang]

On  Monday, February 1, 2016 4:18 PM, Herbert Xu wrote:
>
> On Wed, Jan 27, 2016 at 05:08:35PM +0800, Rui Wang wrote:
>>
>> +static int sha1_mb_async_import(struct ahash_request *req, const void 
>> +*in) {
>> +	struct ahash_request *mcryptd_req = ahash_request_ctx(req);
>> +	struct crypto_ahash *tfm = crypto_ahash_reqtfm(req);
>> +	struct sha1_mb_ctx *ctx = crypto_ahash_ctx(tfm);
>> +	struct mcryptd_ahash *mcryptd_tfm = ctx->mcryptd_tfm;
>> +	struct crypto_shash *child = mcryptd_ahash_child(mcryptd_tfm);
>> +	struct mcryptd_hash_request_ctx *rctx;
>> +	struct shash_desc *desc;
>> +	int err;
>> +
>> +	memcpy(mcryptd_req, req, sizeof(*req));
>> +	ahash_request_set_tfm(mcryptd_req, &mcryptd_tfm->base);
>> +	rctx = ahash_request_ctx(mcryptd_req);
>> +	desc = &rctx->desc;
>> +	desc->tfm = child;
>> +	desc->flags = CRYPTO_TFM_REQ_MAY_SLEEP;
>> +
>> +	err = crypto_shash_init(desc);
>> +	if (err)
>> +		return err;
>
> What is this desc for?

Hi Herbert,

Yeah I just realized that the call to crypto_shash_init() isn't necessary
here. What it does is overwritten by crypto_ahash_import(). But this desc
still needs to be initialized here because it's newly allocated by
ahash_request_alloc(). We eventually calls the shash version of import()
which needs desc as an argument. The real context to be imported is then
derived from shash_desc_ctx(desc).

desc is a sub-field of struct mcryptd_hash_request_ctx, which is again a
sub-field of the bigger blob allocated by ahash_request_alloc(). The entire
blob's size is set in sha1_mb_async_init_tfm(). So a better version is as
follows:

(just removed the call to crypto_shash_init())