linux-kernel - Re: [bug] crypto/vmx/p8_ghash memory corruption in 4.8-rc7

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Date:   Mon, 26 Sep 2016 14:43:17 -0300
From:   Marcelo Cerri <marcelo.cerri@...onical.com>
To:     Herbert Xu <herbert@...dor.apana.org.au>
Cc:     Jan Stancek <jstancek@...hat.com>, rui.y.wang@...el.com,
        mhcerri@...ux.vnet.ibm.com, leosilva@...ux.vnet.ibm.com,
        pfsmorigo@...ux.vnet.ibm.com, linux-crypto@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [bug] crypto/vmx/p8_ghash memory corruption in 4.8-rc7

Herbert,

Wouldn't be enough to provide a pair of import/export functions as the
padlock-sha driver does?

-- 
Regards,
Marcelo

On Mon, Sep 26, 2016 at 10:59:34PM +0800, Herbert Xu wrote:
> On Fri, Sep 23, 2016 at 08:22:27PM -0400, Jan Stancek wrote:
> >
> > This seems to directly correspond with:
> >   p8_ghash_alg.descsize = sizeof(struct p8_ghash_desc_ctx) == 56
> >   shash_tfm->descsize = sizeof(struct p8_ghash_desc_ctx) + crypto_shash_descsize(fallback) == 56 + 20
> > where 20 is presumably coming from "ghash_alg.descsize".
> > 
> > My gut feeling was that these 2 should match, but I'd love to hear
> > what crypto people think.
> 
> Indeed.  The vmx driver is broken.  It is allocating a fallback
> but is not providing any space for the state of the fallback.
> 
> Unfortunately our interface doesn't really provide a way to provide
> the state size dynamically.  So what I'd suggest is to fix the
> fallback to the generic ghash implementation and export its state
> size like we do for md5/sha.
> 
> 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
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