linux-kernel - Re: [PATCH v3 0/7] crypto: x86: Fix indirect function call casts

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Message-ID: <CAGXu5jL7pWWXuJMinghn+3GjQLLBYguEtwNdZSQy++XGpGtsHQ@mail.gmail.com>
Date:   Tue, 7 May 2019 14:07:51 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Herbert Xu <herbert@...dor.apana.org.au>,
        Joao Moreira <jmoreira@...e.de>,
        Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>, X86 ML <x86@...nel.org>,
        linux-crypto <linux-crypto@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Kernel Hardening <kernel-hardening@...ts.openwall.com>
Subject: Re: [PATCH v3 0/7] crypto: x86: Fix indirect function call casts

On Tue, May 7, 2019 at 10:00 AM Eric Biggers <ebiggers@...nel.org> wrote:
> > Given the above, the current efforts to improve the Linux security,
> > and the upcoming kernel support to compilers with CFI features, this
> > creates macros to be used to build the needed function definitions,
> > to be used in camellia, cast6, serpent, twofish, and aesni.
>
> So why not change the function prototypes to be compatible with common_glue_*_t
> instead, rather than wrapping them with another layer of functions?  Is it
> because indirect calls into asm code won't be allowed with CFI?

I don't know why they're not that way to begin with. But given that
the casting was already happening, this is just moving it to a place
where CFI won't be angry. :)

> >   crypto: x86/crypto: Use new glue function macros
>
> This one should be "x86/serpent", not "x86/crypto".

Oops, yes, that's my typo. I'll fix for v4. Do the conversions
themselves look okay (the changes are pretty mechanical)? If so,
Herbert, do you want a v4 with the typo fix, or do you want to fix
that up yourself?

Thanks!

-- 
Kees Cook