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Date: Wed, 14 Dec 2016 12:56:14 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Andy Lutomirski <luto@...capital.net>
Cc: Eric Biggers <ebiggers3@...il.com>, linux-crypto@...r.kernel.org,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"linux-mm@...ck.org" <linux-mm@...ck.org>,
"kernel-hardening@...ts.openwall.com" <kernel-hardening@...ts.openwall.com>,
Andrew Lutomirski <luto@...nel.org>,
Stephan Mueller <smueller@...onox.de>
Subject: Re: Remaining crypto API regressions with CONFIG_VMAP_STACK
On Tue, Dec 13, 2016 at 09:06:31AM -0800, Andy Lutomirski wrote:
>
> > Having 0 as type and CRYPTO_ALG_ASYNC as mask in general means
> > that we're requesting a sync algorithm (i.e., ASYNC bit off).
> >
> > However, it is completely unnecessary for shash as they can never
> > be async. So this could be changed to just ("michael_mic", 0, 0).
>
> I'm confused by a bunch of this.
>
> 1. Is it really the case that crypto_alloc_xyz(..., CRYPTO_ALG_ASYNC)
> means to allocate a *synchronous* transform? That's not what I
> expected.
crypto_alloc_xyz(name, 0, CRYPTO_ALG_ASYNC) allocates a sync tfm
and crypto_alloc_xyz(name, CRYPTO_ALG_ASYNC, CRYPTO_ALG_ASYNC)
allocates an async tfm while crypto_alloc_xyz(name, 0, 0) does
not care whether the allocated tfm is sync or asnc.
> 2. What guarantees that an async request is never allocated on the
> stack? If it's just convention, could an assertion be added
> somewhere?
Sure we can add an assertion.
Cheers,
--
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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