linux-kernel - Re: [RFC PATCH v4] akcipher: new verify API for public key algorithms

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Date:   Mon, 4 Feb 2019 17:00:40 +0300
From:   Vitaly Chikunov <vt@...linux.org>
To:     Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        David Howells <dhowells@...hat.com>,
        Maxime Coquelin <mcoquelin.stm32@...il.com>,
        Alexandre Torgue <alexandre.torgue@...com>,
        Horia Geantă <horia.geanta@....com>,
        Aymen Sghaier <aymen.sghaier@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Gary Hook <gary.hook@....com>,
        Giovanni Cabiddu <giovanni.cabiddu@...el.com>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org,
        keyrings@...r.kernel.org, linux-stm32@...md-mailman.stormreply.com,
        linux-arm-kernel@...ts.infradead.org, qat-linux@...el.com
Subject: Re: [RFC PATCH v4] akcipher: new verify API for public key algorithms

Herbert,

On Fri, Feb 01, 2019 at 10:09:23AM +0300, Vitaly Chikunov wrote:
> On Fri, Feb 01, 2019 at 02:26:55PM +0800, Herbert Xu wrote:
> > On Fri, Jan 25, 2019 at 09:01:16PM +0300, Vitaly Chikunov wrote:
> > >
> > > @@ -781,36 +780,17 @@ static int tpm_key_verify_signature(const struct key *key,
> > >  	if (!req)
> > >  		goto error_free_tfm;
> > >  
> > > -	ret = -ENOMEM;
> > > -	outlen = crypto_akcipher_maxsize(tfm);
> > > -	output = kmalloc(outlen, GFP_KERNEL);
> > > -	if (!output)
> > > -		goto error_free_req;
> > > -
> > > -	sg_init_one(&sig_sg, sig->s, sig->s_size);
> > > -	sg_init_one(&digest_sg, output, outlen);
> > > -	akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
> > > -				   outlen);
> > > +	sg_init_table(&src_sg, 2);
> > > +	sg_set_buf(&src_sg[0], sig->s, sig->s_size);
> > > +	sg_set_buf(&src_sg[1], sig->digest, sig->digest_size);
> > > +	akcipher_request_set_crypt(req, &src_sg, NULL, sig->s_size,
> > > +				   sig->digest_size);
> > 
> > It's not clear that sig->digest is guaranteed to be kmalloc memory.
> > In any case, it's best not to mix unrelated changes in a single
> > patch.  So please keep the kmalloc on output and then copy
> > sig->digest into it and put output into the SG list.

I will do that.

Thanks,

> It is not guaranteed that sig->s will be kmalloc memory either. (Except
> we know it for sure like we know the same about sig->digest).
> 
> You can see in public_key_signature_free() that both fields are kfree'd
> together.
> 
> So, I don't understand why we should treat sig->digest differently than
> sig->s.
> 
> I was just removing kmalloc'ed output as crypto_akcipher_verify() does
> not need any output anymore. So, it's not some sort of mixing unrelated
> changes, from my point of view.
> 
> Thanks,
> 
> > 
> > Thanks,
> > -- 
> > 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