linux-kernel - Re: [PATCH] crypto: x86/polyval - Fix crashes when keys are not 16-byte aligned

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Date:   Mon, 17 Oct 2022 16:38:25 -0700
From:   Nathan Huckleberry <nhuck@...gle.com>
To:     Eric Biggers <ebiggers@...nel.org>
Cc:     Bruno Goncalves <bgoncalv@...hat.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>, Ard Biesheuvel <ardb@...nel.org>,
        linux-crypto@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] crypto: x86/polyval - Fix crashes when keys are not
 16-byte aligned

On Mon, Oct 17, 2022 at 4:02 PM Eric Biggers <ebiggers@...nel.org> wrote:
>
> On Mon, Oct 17, 2022 at 03:26:20PM -0700, Nathan Huckleberry wrote:
> > The key_powers array is not guaranteed to be 16-byte aligned, so using
> > movaps to operate on key_powers is not allowed.
> >
> > Switch movaps to movups.
> >
> > Fixes: 34f7f6c30112 ("crypto: x86/polyval - Add PCLMULQDQ accelerated implementation of POLYVAL")
> > Reported-by: Bruno Goncalves <bgoncalv@...hat.com>
> > Signed-off-by: Nathan Huckleberry <nhuck@...gle.com>
> > ---
> >  arch/x86/crypto/polyval-clmulni_asm.S | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/x86/crypto/polyval-clmulni_asm.S b/arch/x86/crypto/polyval-clmulni_asm.S
> > index a6ebe4e7dd2b..32b98cb53ddf 100644
> > --- a/arch/x86/crypto/polyval-clmulni_asm.S
> > +++ b/arch/x86/crypto/polyval-clmulni_asm.S
> > @@ -234,7 +234,7 @@
> >
> >       movups (MSG), %xmm0
> >       pxor SUM, %xmm0
> > -     movaps (KEY_POWERS), %xmm1
> > +     movups (KEY_POWERS), %xmm1
> >       schoolbook1_noload
> >       dec BLOCKS_LEFT
> >       addq $16, MSG
>
> I thought that crypto_tfm::__crt_ctx is guaranteed to be 16-byte aligned,
> and that the x86 AES code relies on that property.
>
> But now I see that actually the x86 AES code manually aligns the context.
> See aes_ctx() in arch/x86/crypto/aesni-intel_glue.c.
>
> Did you consider doing the same for polyval?

I'll submit a v2 aligning the tfm_ctx. I think that makes more sense
than working on unaligned keys.

Is there a need to do the same changes on arm64? The keys are also
unaligned there.

>
> If you do prefer this way, it would be helpful to leave a comment for
> schoolbook1_iteration that mentions that the unaligned access support of
> vpclmulqdq is being relied on, i.e. pclmulqdq wouldn't work.
>
> - Eric

Thanks,
Huck