linux-kernel - Re: [PATCH v1 1/3] crypto: caam - add in-kernel interface for blob generator

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Date:   Tue, 23 Mar 2021 17:41:06 +0100
From:   Ahmad Fatoum <a.fatoum@...gutronix.de>
To:     Horia Geantă <horia.geanta@....com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>
Cc:     "kernel@...gutronix.de" <kernel@...gutronix.de>,
        James Bottomley <jejb@...ux.ibm.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        Mimi Zohar <zohar@...ux.ibm.com>,
        David Howells <dhowells@...hat.com>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Udit Agarwal <udit.agarwal@....com>,
        Jan Luebbe <j.luebbe@...gutronix.de>,
        David Gstir <david@...ma-star.at>,
        Franck Lenormand <franck.lenormand@....com>,
        Sumit Garg <sumit.garg@...aro.org>,
        "linux-integrity@...r.kernel.org" <linux-integrity@...r.kernel.org>,
        "keyrings@...r.kernel.org" <keyrings@...r.kernel.org>,
        "linux-crypto@...r.kernel.org" <linux-crypto@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-security-module@...r.kernel.org" 
        <linux-security-module@...r.kernel.org>
Subject: Re: [PATCH v1 1/3] crypto: caam - add in-kernel interface for blob
 generator

Hello Horia,

On 21.03.21 21:46, Horia Geantă wrote:
> On 3/16/2021 7:01 PM, Ahmad Fatoum wrote:
>> +	init_job_desc(desc, 0);
>> +	append_key_as_imm(desc, keymod, keymod_len, keymod_len,
>> +			  CLASS_2 | KEY_DEST_CLASS_REG);
>> +	append_seq_in_ptr(desc, dma_in, length - CAAM_BLOB_OVERHEAD, 0);
>> +	append_seq_out_ptr(desc, dma_out, length, 0);
> In case length is known to be < 2^16, it's recommended to use instead
> append_seq_in_ptr_intlen, append_seq_out_ptr_intlen.

Didn't know about this one. Will look into using it for v2.

>> +#define CAAM_BLOB_KEYMOD_LENGTH		16
> The define isn't used here or on patch 3/3.

Will drop and adjust the function docs to note the maximum modifier length.


>> +#define CAAM_BLOB_OVERHEAD		(32 + 16)
>> +#define CAAM_BLOB_MAX_LEN		4096
>> +
>> +struct caam_blob_priv;
>> +
>> +/** caam_blob_gen_init - initialize blob generation
>> + *
>> + * returns either pointer to new caam_blob_priv instance
>> + * or error pointer
>> + */
>> +struct caam_blob_priv *caam_blob_gen_init(void);
>> +
>> +/** caam_blob_gen_init - free blob generation resources
>> + *
>> + * @priv: instance returned by caam_blob_gen_init
>> + */
>> +void caam_blob_gen_exit(struct caam_blob_priv *priv);
>> +
>> +/** caam_encap_blob - encapsulate blob
>> + *
>> + * @priv:   instance returned by caam_blob_gen_init
>> + * @keymod: string to use as key modifier for blob encapsulation
>> + * @input:  buffer which CAAM will DMA from
>> + * @output: buffer which CAAM will DMA to
> Is it guaranteed that input, output can be DMA-mapped?

It's expected callers ensure that this is the case. Trusted key buffers
are allocated with kmalloc and can be DMA-mapped.

Thanks for the review,
Ahmad

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