[dm-devel] [PATCH v2 10/11] crypto: ahash: Remove VLA usage for AHASH_REQUEST_ON_STACK

[Herbert Xu]

On Mon, Jun 25, 2018 at 03:56:09PM -0700, Eric Biggers wrote:
>
> > diff --git a/include/crypto/internal/hash.h b/include/crypto/internal/hash.h
> > index a0b0ad9d585e..d96ae5f52125 100644
> > --- a/include/crypto/internal/hash.h
> > +++ b/include/crypto/internal/hash.h
> > @@ -142,6 +142,7 @@ static inline struct ahash_alg *__crypto_ahash_alg(struct crypto_alg *alg)
> >  static inline void crypto_ahash_set_reqsize(struct crypto_ahash *tfm,
> >  					    unsigned int reqsize)
> >  {
> > +	BUG_ON(reqsize > AHASH_MAX_REQSIZE);
> >  	tfm->reqsize = reqsize;
> >  }
> 
> This isn't accounting for the cases where a hash algorithm is "wrapped" with
> another one, which increases the request size.  For example, "sha512_mb" ends up
> with a request size of

I think this patch is on the wrong track.  The stack requests are
only ever meant to be used for synchronous algorithms (IOW shash
algorithms) and were a quick-and-dirty fix for legacy users.

So either check SHASH_MAX_REQSIZE or just convert the users to
kmalloc or even better make them real async users.

Cheers,
-- 
Email: Herbert Xu <herbert at gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt