linux-kernel - Re: [BUG] SLOB breaks Crypto

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Date:	Tue, 18 May 2010 14:06:20 -0500
From:	Matt Mackall <mpm@...enic.com>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	Adrian-Ken Rueegsegger <ken@...elabs.ch>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	michael-dev@...i-braun.de, Pekka Enberg <penberg@...helsinki.fi>,
	linux-kernel@...r.kernel.org, linux-crypto@...r.kernel.org,
	Atsushi Nemoto <anemo@....ocn.ne.jp>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: [BUG] SLOB breaks Crypto

On Tue, 2010-05-18 at 20:27 +1000, Herbert Xu wrote:
> On Tue, May 18, 2010 at 10:17:35AM +0200, Adrian-Ken Rueegsegger wrote:
> > 
> > As noted in my other mail [1] it seems like the HMAC tests trigger these
> > errors.
> 
> Thanks for all the detective work!
> 
> I think the problem is this changeset:
> 
> commit 6eb7228421c01ba48a6a88a7a5b3e71cfb70d4a9
> Author: Herbert Xu <herbert@...dor.apana.org.au>
> Date:   Tue Jan 8 17:16:44 2008 +1100
> 
>     [CRYPTO] api: Set default CRYPTO_MINALIGN to unsigned long long
>     
>     Thanks to David Miller for pointing out that the SLAB (or SLOB/SLUB)
>     cache uses the alignment of unsigned long long if the architecture
>     kmalloc/slab alignment macros are not defined.
>     
>     This patch changes the CRYPTO_MINALIGN so that it uses the same default
>     value.
>     
>     Signed-off-by: Herbert Xu <herbert@...dor.apana.org.au>
> 
> diff --git a/include/linux/crypto.h b/include/linux/crypto.h
> index 0aba104..5e02d1b 100644
> --- a/include/linux/crypto.h
> +++ b/include/linux/crypto.h
> @@ -90,13 +90,11 @@
>  #define CRYPTO_MINALIGN ARCH_KMALLOC_MINALIGN
>  #elif defined(ARCH_SLAB_MINALIGN)
>  #define CRYPTO_MINALIGN ARCH_SLAB_MINALIGN
> +#else
> +#define CRYPTO_MINALIGN __alignof__(unsigned long long)
>  #endif
>  
> -#ifdef CRYPTO_MINALIGN
>  #define CRYPTO_MINALIGN_ATTR __attribute__ ((__aligned__(CRYPTO_MINALIGN)))
> -#else
> -#define CRYPTO_MINALIGN_ATTR
> -#endif
>  
>  struct scatterlist;
>  struct crypto_ablkcipher;
> 
> So evidently the assumption made in this change does not work on
> SLOB since it only guarantees __alignof__(unsigned long).

Bingo. Feel free to stick this on your revert:

Acked-by: Matt Mackall <mpm@...enic.com>

Looks like we should ensure that ARCH_KMALLOC_MINALIGN is always
defined.

-- 
Mathematics is the supreme nostalgia of our time.


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