linux-kernel - Re: [PATCH v3 1/3] big key: get rid of stack array allocation

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Message-ID: <alpine.LRH.2.21.1805100519200.12749@namei.org>
Date:   Thu, 10 May 2018 05:19:31 +1000 (AEST)
From:   James Morris <jmorris@...ei.org>
To:     Kees Cook <keescook@...omium.org>
cc:     Tycho Andersen <tycho@...ho.ws>,
        David Howells <dhowells@...hat.com>, keyrings@...r.kernel.org,
        linux-security-module <linux-security-module@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        "Jason A . Donenfeld" <Jason@...c4.com>,
        Eric Biggers <ebiggers3@...il.com>
Subject: Re: [PATCH v3 1/3] big key: get rid of stack array allocation

On Tue, 8 May 2018, Kees Cook wrote:

> On Tue, Apr 24, 2018 at 1:26 PM, Tycho Andersen <tycho@...ho.ws> wrote:
> > We're interested in getting rid of all of the stack allocated arrays in the
> > kernel [1]. This patch simply hardcodes the iv length to match that of the
> > hardcoded cipher.
> >
> > [1]: https://lkml.org/lkml/2018/3/7/621
> >
> > v2: hardcode the length of the nonce to be the GCM AES IV length, and do a
> >     sanity check in init(), Eric Biggers
> > v3: * remember to free big_key_aead when sanity check fails
> >     * define a constant for big key IV size so it can be changed along side
> >       the algorithm in the code
> >
> > Signed-off-by: Tycho Andersen <tycho@...ho.ws>
> > CC: David Howells <dhowells@...hat.com>
> > CC: James Morris <jmorris@...ei.org>
> > CC: "Serge E. Hallyn" <serge@...lyn.com>
> > CC: Jason A. Donenfeld <Jason@...c4.com>
> > CC: Eric Biggers <ebiggers3@...il.com>
> 
> Please consider this and patches 2 and 3:
> 
> Reviewed-by: Kees Cook <keescook@...omium.org>
> 
> James, are these something you can take into your tree?

> 
> Thanks!
> 
> -Kees
> 
> > ---
> >  security/keys/big_key.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> >
> > diff --git a/security/keys/big_key.c b/security/keys/big_key.c
> > index 933623784ccd..2806e70d7f8f 100644
> > --- a/security/keys/big_key.c
> > +++ b/security/keys/big_key.c
> > @@ -22,6 +22,7 @@
> >  #include <keys/user-type.h>
> >  #include <keys/big_key-type.h>
> >  #include <crypto/aead.h>
> > +#include <crypto/gcm.h>
> >
> >  struct big_key_buf {
> >         unsigned int            nr_pages;
> > @@ -85,6 +86,7 @@ struct key_type key_type_big_key = {
Sure!

-- 
James Morris
<jmorris@...ei.org>