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Date:   Fri, 21 Aug 2020 14:24:43 +1000
From:   Herbert Xu <herbert@gondor.apana.org.au>
To:     Eric Biggers <ebiggers@kernel.org>
Cc:     lenaptr@google.com, linux-crypto@vger.kernel.org,
        smueller@chronox.de, ardb@kernel.org, jeffv@google.com
Subject: Re: [PATCH v5] crypto: af_alg - add extra parameters for DRBG
 interface
Message-ID: <20200821042443.GA25695@gondor.apana.org.au>
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Eric Biggers <ebiggers@kernel.org> wrote:
>
> Since proto_ops are almost identical, and only one is used in a given kernel
> build, why not just do:
> 
> static struct proto_ops algif_rng_ops = {
>        ...
> #ifdef CONFIG_CRYPTO_USER_API_RNG_CAVP
>        .sendmsg        = rng_sendmsg,
> #else
>        .sendmsg        = sock_no_sendmsg,
> #endif
>        ...
> };
> 
> Similarly for .recvmsg(), although I don't understand what's wrong with just
> adding the lock_sock() instead...  The RNG algorithms do locking anyway, so it's
> not like that would regress the ability to recvmsg() in parallel.  Also,
> conditional locking depending on the kernel config makes it more difficult to
> find kernel bugs like deadlocks.

I want this to have minimal impact on anyone who's not using it.
After all, this is something that only Google is asking for.

Anyway, I wasn't looking for a compile-time ops switch, but a
run-time one.

I think what we can do is move the new newsock->ops assignment
in af_alg_accept up above the type->accept call which would then
allow it to be overridden by the accept call.

After that you could just change newsock->ops depending on whether
pctx->entropy is NULL or not in rng_accept_parent.

As for the proto_ops duplication I don't think it's that big a
deal, but if you're really bothered just create a macro for the
identical bits in the struct.

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